Even legends like Mary Berry sometimes get thrown.

“I’ve had many disasters in the kitchen,” the 87-year-old admits – but she sounds so self-assured, you can’t imagine her getting knocked off course for too long.

For Berry, surprises tend to come in the form of her children, Annabel and Thomas (her other son William died age 19) and five grandchildren turning up for dinner unexpectedly. It seems no one is that fond of phoning ahead.

“Very often I have family coming round, lots of young [people] – and then two more turn up.” Adding with cheeky groan: “I know exactly what they’re like, and they’re very hungry.”

But she certainly seems to relish being surrounded by her family – and she has a few nifty tricks up her sleeve for catering when unexpected guests turn up. “If it’s a big pot of something, I’ll add another can of flageolet beans or black-eyed beans or even a can of baked beans, to spin it out – which is what we have to do.”

Many families will be thinking of ways to stretch their meals further, as food and energy prices continue to soar – and Berry’s top piece of advice for cutting costs in the kitchen is all about preparation. “I think saving money on cooking is being organised, and a bit of planning beforehand,” she says. “If you’ve got people coming round – relations, friends, whatever – it’s doing the shopping list and not veering from it.”

Berry might seem as put together as it gets, but she hasn’t always been the pinnacle of organisation. “I’ve learned it over the years,” she says – and practise makes perfect. “If I’ve gone to the trouble, which indeed, I did at the weekend – I did two roast chickens, which is one of the recipes in the book. I made really good stock – really good gravy, far too much for that day, and I froze the rest. That means when you’ve maybe just got a chicken breast and you want to have gravy with it, you’ve got it in the freezer.

“I don’t waste anything. If there’s something left, I usually freeze it.”

While Berry’s style is definitely classic, she’s slowly but surely incorporating newer ingredients into her food vocabulary – largely thanks to her family members. She says: “At the moment they’re all at the age where they eat a lot, and they like very much trying new things – so I use more of the ingredients they enjoy the most.”

That means you’ll see a lot more avocados in Berry’s recipes than you might have previously, along with other family favourites, including beans, lentils and chickpeas. “They’re willing to try anything,” she adds.

Many of these ingredients feature in her latest book, Cook And Share, which very much does what it says on the tin, and puts sharing food centre. Berry suggests food has become more laid-back, and her recipes reflect this.

“I wanted it to be more relaxed – sharing, help yourself, and still [thinking] what I can prepare ahead,” she says. “Most people are working, and they can’t always do everything just before friends are coming round.”

At 87, Berry shows no sign of slowing down – her new book is accompanied by a BBC series of the same name – so she’s eager to make life easier for everyone in her recipes. “I do quite a bit of preparing ahead, just adding something at the last minute,” she says – whether that’s fresh herbs or another garnish to bring the dish to life.

Fans of Berry’s recipes won’t be disappointed by her latest offering. “There are some classic things that I’ve relooked at,” she says. “We’ve got the ultimate chocolate brownie – that’s to die for. I’ve done many brownie recipes and blondies and things in my time, but we’ve put the ultimate chocolate brownie in there, and a few casseroles – the Sunday best minted lamb is delicious… Then there’s one pot things like Tuscan chicken, which is the sort of dish you can share for a very special occasion. It’s done with chicken thighs, which if you overcook and people are late – it doesn’t matter a bit, it just means it is more tender. Whereas if we use the breasts, it would have become tough.”

She’s always a fan of the classics, but Berry isn’t afraid to branch out either, saying: “We’ve included brunch this time, because brunch seems to be very popular – especially on a Sunday morning, when you have friends round,” she adds. “Perhaps they don’t necessarily want to do a roast – they do brunch, because everybody gets up a bit later, and it’s a lovely meal to share.”

Berry might see the appeal of brunch, but that doesn’t mean she’s completely ditched her Sunday routine. “In our family, it’s still the Sunday roast,” she admits. “But of course, this summer’s been so warm, we’ve often had brunch instead.”

Cook And Share by Mary Berry is published in hardback by BBC Books, priced £27. Photography by Laura Edwards. Available now.