Why is it so exciting – and so nerve-racking – to be meeting Delia Smith? Down the years, I’ve interviewed a lot of famous and important people (and three prime ministers), and yet I can’t remember any of them having induced this combination of extreme eagerness and mortal fear. Is it because when I was a teenager, she was one of the very few truly successful women then in public life? I suppose it must be. It’s no exaggeration to say that she was up there with the Queen, Mrs Thatcher and Madonna – and just like them, her word was The Law. For my 21st birthday, my parents gave me a cheque and a copy of Delia Smith’s Complete Cookery Course, and for all that I was still in my radical feminist stage, I hardly batted an eyelid. Simone de Beauvoir was all very well, but did she have any advice on roasting times or how to make sure your yorkshire puddings rise? No, she did not.

Anyway, one result of this desperate, anxious state was that I stupidly decided to bake a cake for her – my God, even to write such words – and when I arrive at her cottage, the conservatory of which I recognise from the TV shows she once presented there, the very first thing I do is hand it over. “It’s a bit … flat,” I say, mournfully (for those who are interested, it’s Nigella’s ordinarily easy-peasy cardamon and marzipan loaf). But it seems that I’m worrying unnecessarily. Delia looks completely delighted by my foil-wrapped house brick, cradling it in her arms as if it was a newborn baby. “You used good ingredients,” she says, kindly. “It will still taste nice.” Cooking isn’t about perfection, she tells me; it’s about achievability. “I once went to a Women’s Institute thing, and I remember thinking: I’m not at all sure my jam would pass muster here.”

It’s a beautiful, crystalline day in Suffolk – the house is deep in the countryside outside Stowmarket – and from the sofa, the view is of a pond, on which there floats a single, serene moorhen, and beyond it a line of trees. Delia and her husband, the journalist Michael Wynn-Jones, have lived here since the 1970s, but this expanse of garden is a relatively recent addition: 20 years ago, he bought the meadow as a present for her 60th birthday, and together (with some help, obviously) they sunk the pond. Was it a blessing during the lockdown? “Oh, yes. We’re very lucky. The pandemic has been terrible for so many people, but it wasn’t a hardship for us. We’re older, and we live in a beautiful place. I have an office at the bottom of the garden, and I was there every day from 9.30.” Lunch was an apple, and then, at 5.30, she would return to the house, to a supper made by Michael, who now does most of the cooking. Is he a good cook? “Yes, if he follows the recipe. When he retired, he got really interested in it. He wanted to do more and more, and I let him do more and more, though I do still love cooking and, of course, food. You’ve got to be greedy to love cooking, and I always have been. The first thing I do in the morning when I get up is think: what are we going to eat today? And I’m lucky to be married to someone who feels the same way. But cooking is the one time when I know I’m 80: all that standing, getting a backache.”

How on earth can she possibly be 80? In the flesh, she looks exactly as she did the last time we saw her on screen, more than a decade ago, and perhaps even before that. Close your eyes, moreover, and this is still the voice, crisp and light and warm, that once drove us all so mad for cranberries (Delia Smith’s Winter Collection, 1995). But there’s something else, too: she is so interested in everything, enthusiasm and energy radiating from her like steam from a pan. As all the world knows, she and Michael have long been majority shareholders in their beloved Norwich City football club, and her involvement there is still all-consuming. There are its restaurants, which she oversees, and every week there are dozens of management decisions to be taken; above all, there are the matches, her appetite for which remains undimmed. “Yes, I’m afraid so. Three hours there and three hours back, sometimes. Often, there’ll be a game on a Tuesday and I might say: ‘I’m not going.’ But then Monday will come and I’ll think: ‘Actually, I am. I can’t not go.’” For her, football is about community; she believes almost anything is possible when people commit to working together, though admittedly this may not stretch to poor old Norwich’s ability to remain in the Premiership come the end of this season.

Which brings us to her new book, the one she wrote while she was sequestered in her office at the bottom of the garden. It also has to do with community. As its title suggests, You Matter: The Human Solution is not a cookbook. Rather, it is (sorry) an extended recipe for living: a nourishing broth of ideas garnered from her wide reading (its presiding spirits are the Jesuit priest and palaeontologist Pierre Teilhard de Chardin, the Holocaust survivor and psychiatrist Viktor Frankl, and the American psychologist Abraham Maslow), seasoned lightly with her own thoughts and experiences. How to sum it up? This is tricky. It has, I think, three central premises. First, that we have not yet fully perceived just how awesome the human race is, and as a consequence we underestimate our ability to come up with solutions to our increasingly grave problems. Second, that evolution encompasses, for human beings, a trajectory of unity, one we resist at our peril. Third, that we often neglect our inner, spiritual selves, and by doing so, tend to lose our all-important sense of perspective, something that has an egregious effect on our ability even to begin to tackle the mayhem that is all around.

Has Delia gone barmy? This is surely what some people are going to say when they hear about this book, and perhaps you’re thinking it even as you read this. But she doesn’t care if they do. “I’ve had a good apprenticeship when it comes to criticism,” she says. “Because I was very criticised when I was a cook. When people tell me I’m going to get a lot of flak, I think, well, no one wants to take a risk; no one wants to put their head above the parapet. This book could just sink without trace. But if it does, I won’t mind. I had to do it. I want people to know this stuff.” One of the practices she extols in You Matter is silent meditation – though she doesn’t use the m-word, on the grounds it might put people off – and the hour she spends each day sitting completely still as her mind roams where it will has brought her a kind of freedom. “Silence and stillness have taken my fear away,” she says, her voice as calm and as soothing as a bowl of custard.

When did she start thinking about these ideas? “Well, they were always bubbling around, and I did write some religious books at one stage [a Catholic convert, she used to go to mass every day; the books in question were published in the 1980s]. But I found they just went to religious people, and I wanted to write for those who don’t have any religion. The main thrust of it is that there is a whole part of our lives that is left unexplored, and this is the crucial time in our history to get into that. Things are very bad. How could we not want to look at the world and say: we’ve got to change?” A pause. “Have you seen Don’t Look Up?” she asks. I shake my head. (In case you don’t know, it’s a Netflix film starring Leonardo DiCaprio and Jennifer Lawrence, about a comet that’s heading towards Earth, a calamity that is an allegory for the climate emergency]. “Well, it’s brilliant, and it’s also saying what I’m saying, which is that we don’t realise the power we have when we work together.”

Before I read You Matter, I hadn’t heard of Pierre Teilhard de Chardin, a man she describes as “a colossus” (he died in 1955). But she’s not surprised. De Chardin was a Darwinist who fell out with the church over the doctrine of original sin: “All his books were banned by the church for a time,” she says. She got into him in the 1960s. “They’re quite difficult to read. But the more mature I got, the more I realised that humanity is a phenomenon, which is what he says.” The title of her book, however, was not inspired by him, but by a piece torn from a magazine many years ago: the work of a young woman, Dorothea Lynch, who was dying of cancer (Lynch would go on to write a book, Exploding Into Life). It doesn’t always, Delia believes, take a philosopher to spell out the essence of complicated ideas. Lynch was suffering terribly, but in her pain she was able to grasp the beauty of life as never before. “Each of us is very special, very singular, carrying weight,” she wrote. “I matter. I would like to open the window tonight and yell that outside. I matter.”

Delia wishes we could all start thinking this way long before we lie dying – and this is where (she hopes) her book comes in. “The world is in chaos. We have got the war in Ukraine, concentration camps again, people freezing and starving. In our own country, some people can have heat, or they can have food… and yet, together, we have such power. People say to me: how can you get the whole world on board? Well, how did Christians get so many people on board? They were just a little band. Or Muslims? Another little band. So I can’t be put off by that. I’m very ambitious.” Her grand dream is to help her readers to achieve self-actualisation, which according to another of her gurus, Maslow, is the highest level of psychological development: the stage in life when potential may be fully realised, the rest of our needs (those that connect to our bodies and to our egos) having already been fulfilled.

One of the ways such a state may be encouraged is via what she calls “reflective daydreaming”: that daily hour of silence she mentioned earlier. When, many years ago, she started doing this, inspired by an Indian sufi, she began slowly, clocking in 10 minutes or so at first. “It’s not easy,” she says. “It’s the hardest thing on earth to get someone to be still and quiet. But I just feel that there will be some people who will want to try it, and if we get enough people like that, the world will change.” The Beatles song Within You Without You pretty much sums up her book, she says. Pay attention to what’s inside, as well as what’s outside, and life will be better. “Let’s get away from the idea of me as a saint. I make as many mistakes as anyone. I’m always saying the wrong thing. These ideas are not virtue on my part. I just want to connect.”

What has the response to the book been like so far? Michael scrutinised each section as she completed it. “He would say: ‘OK’. Or: ‘I don’t think you’ve got that quite right.’” But You Matter was turned down by no fewer than six publishers, in spite of the fact that Delia has sold more than 21m copies of her cookbooks. “It was tough. At one point we were looking at self-publishing.” Finally, it went to a small press: Mensch. “And thank God those six did turn it down. I couldn’t have done better.” I’ve no idea how her latest editor feels about self-actualisation. But he or she will surely have relished the glimpses its author gives of herself on the path to enlightenment. How surprising (and cheering) to find that she loves Pharrell Williams; that she marched against Brexit; that she idolises Greta Thunberg; that it is her great pleasure to take the Norwich apprentices to the Sainsbury Centre for Visual Arts at the University of East Anglia to look at paintings by Bacon and Picasso. (“In the cafeteria, these guys of 16 were collecting up the cups; they’ve been trained to think of others because you can’t become a team if you’re only interested in yourself,” she says, when I bring this up.)

In its exuberance and sincerity, You Matter is emphatically the work of an autodidact, and perhaps this is one way in which it connects, as unlikely as this sounds, to the rest of her career. She left her school in Bexleyheath at 16, and went to work first as a hairdresser. But having grown interested in cooking, at 21 she started again, this time as a dishwasher in a small restaurant in Paddington, a role that gave her the opportunity to learn on the job (eventually, she graduated to waitressing, and thence to the kitchen). Meanwhile, she spent her free time devouring cookbooks in the reading room at the British Museum, trying out the recipes she found on the family from whom she rented a room. In 1969, she was taken on by the Daily Mirror’s magazine, which is where she met Michael; the first thing she wrote was a recipe for kipper paté. From there, she moved to the Evening Standard and into television (her first appearances were on the BBC’s Look East). Again, she learned as she went along. “That was the best job,” she says, of the Standard. “I used to get a lot of letters, and I learned how to write recipes from those. Someone once asked: ‘You say the tomatoes must be peeled, but how?’ From that moment, I never wrote a recipe without explaining every part of the process.”

But she doesn’t miss writing cookbooks or making cookery programmes now. “Some people want more recipes,” she says. “But there are enough. If you’ve gone through your 50th asparagus season, there’s not a lot left to say. I left television when the era of chefs came in; what Elizabeth David called ‘theatre on a plate’, which I can’t stand. I was only about saying: ‘it’s not that difficult’.” Sometimes, she worries about her legacy: are people any better cooks now than they were when she started? “That awful MasterChef thing. You know: ‘Oh, this is a bit greasy,’ or whatever. It’s intimidating. It makes people self-conscious. They feel they’ll never be able to do it.” It’s for this reason that she has put together a cookery course on her website. “It’s the basics. A kid could learn how to make an omelette sitting on the bus.” But at other moments she is reassured. “When I once said that I’d failed [to teach the nation to cook], I got a lot of letters telling me I was wrong, and at football matches people will say: ‘Oh, my mum loves you.’” What about restaurants? Overall, haven’t we gained more than we’ve lost? She’s not sure. “I miss French food. That’s gone.” Do people make a fuss when she eats out? She laughs. “If you think about it, I’m no threat to a chef, though if they do know who I am I feel bad if I leave anything.” This week, she’s going to the Neptune, in Hunstanton, which has a Michelin star. “Usually, that would put me off, but he’s a lovely chef. It’s only slightly poncey.” What’s her favourite dish to make at home? She can’t possibly say, though the Piedmontese peppers from her Summer Collection (1993, as if I could ever forget) “do have to be eaten to be believed”.

A friend of Delia’s who worked with her on the Standard told me that no one could be less changed by fame than her, and it is striking how straightforward she seems, how un-grand. What’s her secret? (I mean, apart from the meditation, and all the other things we’ve discussed). Does it – this is my hunch – have anything to do with her redoubtable mother, Etty, who died in 2020 aged 100? “Yes, that’s probably it. She was calm, too, and she had the same love of people. But she was also my biggest critic. ‘Coo, you’ve put on weight,’ she’d say, that sort of thing. I had quite a difficult time, and my parents’ divorce [when she was a teenager] was a trauma, though no one is without those, are they?” She thinks we have a duty to be happy if we can – or at least, not to be too discontented. But perhaps our terms are wrong. Her late friend Sister Wendy Beckett told her that, in life, “happy” is best substituted with the word “peace”. “That was wise. Happiness can seem like quite a shallow thing, like having a Mars bar or something.”

I’ve missed the train I was supposed to get, and so we talk on. She doesn’t know what she’ll do next: the press “ruined” her last book, How to Cheat at Cooking, in which she extolled the virtues of ready-prepared ingredients like powdered potato, by being “vile” about it. What about Norwich City? No, she and Michael are not selling, though if someone reasonable with money to spend came along, they would ask the supporters to vote on it. She could discuss football for ever, and it’s sweet to see how thrilled she is, still, to meet its biggest names (once my tape recorder is off, she tells me some good stories). And then, at last, it really is time for me to go. Behind the closed door of their kitchen – how I long to look in its cupboards – Michael is clattering slightly.

Back in London, I tell everyone I speak to that I’ve met Delia (no need for second names), and even my mother sounds quite impressed. But I’m still worrying about my cake. In the small hours, I picture her ruthlessly dispatching it, her foot deftly opening a pedal bin as Michael whips up some cheese on toast. Several days later, though, a parcel arrives. Inside it is a signed copy of Delia’s Cakes, and inside that is a card. As I read it, my heart expands inside me like one of her immaculate gooseberry and elderflower muffins. The cake I baked for her was delicious, she writes – and can she please have the recipe?

• You Matter: The Human Solution by Delia Smith is published by Mensch, £25 hardback/£14.99 paperback. To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply