Place the cashews in a heatproof bowl and cover them with boiling water.

Soak the cashews for 10 minutes, then drain them thoroughly.

Preheat the oven to 220°C, 200°C fan, or 425°F.

Peel the Maris Piper potatoes and celeriac, then slice both vegetables into 2 mm / 1/8-inch slices.

Bring a large saucepan of salted water to a boil and add all of the sliced Maris Piper potatoes and celeriac.

Simmer the sliced vegetables for 3 to 4 minutes until just softened.

Drain the par-cooked vegetables and leave them in the colander to steam dry.

Heat 1 teaspoon of olive oil in a large frying pan over medium heat and add the sliced onions.

Fry the onions for 8 to 10 minutes, stirring occasionally, until softened.

Add the grated garlic, chopped fresh rosemary, and cannellini beans to the softened onions.

Fry the onion and bean mixture for 30 seconds, then transfer it to a plate.

Add 1 teaspoon of olive oil to the unwashed frying pan and heat it over medium heat.

Add the shredded kale, a pinch of flaky sea salt, and black pepper to the hot pan.

Cook the kale for 4 to 5 minutes until darkened and reduced in volume.

Put half of the onion and cannellini bean mixture into the high-speed blender.

Add the soaked cashews, vegetable stock, oat milk, nutritional yeast, Dijon mustard, lemon zest, and lemon juice to the blender.

Blend the ingredients until completely smooth and creamy, then season the sauce with a pinch of flaky sea salt.

Arrange a layer of the sliced Maris Piper potatoes and celeriac in a 5 cm / 2-inch deep rectangular baking dish.

Spoon over portions of the remaining onion and cannellini bean mixture, cooked kale, and creamy sauce.

Repeat the vegetable, bean mixture, kale, and sauce layers until all components are used.

Finish with a layer of Maris Piper potatoes and celeriac, then drizzle the top with the remaining olive oil.

Bake the dauphinois for 45 to 50 minutes until golden and until the potatoes and celeriac are fully tender.