Menuwatch: Roof Garden at Pantechnicon

"They were looking for someone with a Nordic background, but with the kids I said I can't do a full-time job," she says. "But they've been really supportive as a mum and a woman. They've been absolutely incredible."

Now Warner is firmly back in the kitchen, overseeing two restaurants at the Nordic-Japanese influenced Pantechnicon in London's Belgravia, which opened in September 2020. Pantechnicon describes itself as an "eating, drinking and shopping village", featuring a number of hospitality operations, including the Sachi Japanese restaurant on the lower ground floor, as well as Café Kitsuné and the Sakaya micro brewer.

"There has historically been a strong trading connection between the Nordics and Japan, and there still is today," explains Warner, who heads up the kitchen at the 90-cover Roof Garden, which provides an entry point to both Japanese and Nordic cooking styles, and the recently opened Eldr Dining Rooms, which see Warner's five-course tasting menu served to around 45 covers three evenings a week.

"Both Nordic and Japanese cultures have a deep respect for nature and minimalism, and their dishes are simple and let the ingredients shine for themselves," she says.

You only have to think of the simplicity of sushi to understand this culinary mindset, while in the Nordics, Warner points to a dish of freshwater crayfish, eaten for only eight weeks in the summer when the crustacean is boiled in water with salt and dill and eaten straight out of the shell or maybe on toast. "You don't mess around with too many flavours," she says.

While she is incorporating cooking styles from two very different nations on a menu, Warner is quick to point out it isn't a fusion restaurant. "The idea is that the dishes are simple and non-intimidating and a good introduction for people who are not too sure what Nordic or Japanese food is like."

Indeed, dishes on the menu tend to be either influenced by Nordic or Japanese, rather than a mix of the two. There are a few exceptions, one being the Arctic char sashimi, sea buckthorn, shichimi (£12), which is a fusion almost by accident. Warner wanted a sashimi dish on the menu, but understandably found it difficult to get hold of sustainable tuna. "Arctic char is what we eat at home, and I found a farm in Devon and it's superb as sashimi," she says.

Mentaiko spaghetti, cod roe, crispy seaweed (£16) – "a sort of Westernised Japanese pasta, which is the ultimate comfort food" – is an example of a traditional Japanese dish, while a distinctly Nordic dish is the Atlantic shrimp, poached trout, potato and charred leek (£16). The influence behind this fish soup is the school dinners Warner typically ate as a child. She cures farmed trout in a traditional gravlax of sugar and salt for 24 hours before cutting it into small cubes that sit in the bottom of the bowl. A fish stock is made from the trout and Arctic char, with vegetables and milk to make a "fishy broth", then poured over the trout which starts to cook in the hot liquid. Potatoes and grilled leeks are also added, and shrimps, trout roe and delicate dill leaves are placed gently on top, while a dill oil is added at the last second to add another burst of flavour.

Clever techniques are dotted throughout Warner's menu, such as the lamb croquette, wild garlic mayonnaise (£14), which is lightly sprayed with a smoked vinegar to cut through the fatty meat "like vinegar on a chip", while the smokiness gives the dish a deep umami flavour.

Desserts see the likes of pandan chiffon cake, rye, wild chervil and apple sorbet (£10), joining the popular bilberry and blue cheese tart, white chocolate, gingerbread (£10). "Desserts are very important to me," says Warner. "In so many great restaurants desserts are often a let-down, so I tried to spend a lot of time on that with our incredibly skilled pastry chef."

Warner describes how she bought in some old Finnish cookbooks for inspiration, and pastry chef Ivan Oleinik came across a blue cheese cheesecake. "The recipe had a horrific picture and sounded revolting," she says. "But he made a beautiful, colourful, fresh-tasting dessert with an ever-so-subtle blue cheese taste." The tart – and the rest of Warner and her team's dishes – are probably as far from revolting as you can possibly get.

19 Motcomb Street, London SW1X 8LB

www.pantechnicon.com/roof-garden