As for her other guests on the show: Reese Witherspoon, Zooming in from America, “was really funny. She had genuinely texted a few months before, saying: ‘I need you to show me something,’ because she’s not a big cook. She was like: ‘I want something family-style that I can cook and put on the table for the kids and everyone will like it.’”

The actress and producer is, it seems, very fun to hang out with. “For me, the kitchen is the centre of the home. Most people hang out in the kitchen more than anywhere else. So guests come into the kitchen, even if it’s a transatlantic version of that. It’s how I like to socialise.”

What about Oprah? How was it flipping the table? Very daunting, admits McCartney. “But then, when I knew what we were going to cook together and I felt confident about it, the rest followed. It brings me back to how food and memories… make you feel good. That’s where the [idea for] whole show came about.”

Surprised to hear that Winfrey had never made a dip, McCartney got creative. “I love Bloody Marys. And I thought: ‘What if you made that into a dip?’ So I tested it with passata, olive oil, and then what you would put in a Bloody Mary: bit of vodka, celery salt, Worcestershire sauce, and heated that through.

“It was more like entertaining Oprah, asking her: ‘What do you like to do? How do you like to greet the guests at a party?’ And she said she likes to meet people at the door with a little shot of good tequila. So more than work, the show is asking, ‘What’s it like at home with you?’”

As for what it’s like at home for McCartney, she and her second husband, director and screenwriter Simon Aboud, have two young sons, Sam, 13, and Sid, 10. From her first marriage she has two older sons, Arthur, 22, and Elliot, 19, both of whom are off at college. All her boys are vegetarian, she says. Really? No cheeky McDonald’s?

“They get the Beyond Meat burger,” she says of the chain’s recently introduced vegan option. “I think that’s been good. Prior to that, I don’t think they were [going to McDonald’s]. But if they were, I wouldn’t have had to go at them. But my tactic is like my mum’s tactic: to make the food as satisfying at home as possible.”

She is, then, always good at making the effort to cook dinner, even if it’s been a knackering day at work. Well, like most of us, she mostly is. “I always will want to,” she begins with a sheepish grin. “But I don’t always. And actually, the thing when my kids would push back is: ‘Can we get a takeaway? Or delivery?’ So, Honest Burger does a really good [veggie option].

“Or we’ll do pizza, or sushi – we’ll just have avocado and cucumber rolls, vegetable tempura rolls. So that’s their way of [rebelling], by eating junk and sweets. “And I’m always trying to push vegetables. I’m like, eat something green!”

When the boys were younger, that found form in another kitchen hack. “I’d do baked beans and put frozen peas in with them!”

A green and orange mush, yum! Thanks, Mum. “No!” she exclaims. “It’s actually quite nice. And then if they don’t want to eat it, you put it all on one piece of toast and you’re done. That was when they were very little, though – and if I wanted to cook something in three minutes!

“The big joke is that my husband says I’m a vegetarian that hates vegetables. I think that’s another reason why I make salads or things with dressings, and soups – ways of eating vegetables where I’m going to enjoy disguising them. Some people love just to eat steamed broccoli.” She wrinkles her nose at the unappetising thought. “I’m like, no. Really good for you, but I’m not that person.”

Serves It Up! has been renewed for a third series, so McCartney is currently developing another batch of recipes. What about guests? “Do you have any ideas for me?” she shoots back.

I suggest Stephen Graham. One of our finest actors, and now with added professional kitchen experience: he’s sensational as a harried chef in the recently released, award-winning film Boiling Point, shot in real time in a real restaurant, Jones & Sons in east London.

“He’d be great. And he’s Scouse! I like a Scouser! I like Jody Comer as well. Maybe we should just do it all around Scousers. Who else is a Scouse?”

Um, apart from your dad? “Yeah. I don’t think Ringo will do it,” she muses of her dad’s old Beatles buddy. “He’s not a big foodie; he doesn’t love food. He’s allergic to onions, and garlic. But he likes a baked potato, and asparagus. He likes hard goat’s cheese! I don’t know how I know this!” she hoots. “But I would be able to cook for him.”

Mary McCartney’s plant-based cooking show Serves It Up! is now available on Discovery+