Sweet Potato Lasagne

Prepare the sweet potato

Heat the oven to 220C (200C fan)/425F/gas 7. Put the slices of sweet potato on a baking tray, add a tablespoon of oil and a quarter-teaspoon of salt, and toss to coat. Arrange on the tray in a single layer, then roast for 20 minutes, until just softening in the middle.

Tomato Sauce

Meanwhile, make the tomato sauce. Put the passata, sun-dried tomato paste, chilli powder, garlic and half a teaspoon of salt in a blender, then blitz smooth. Taste and adjust the seasoning as necessary.

White Sauce

For the white sauce, heat the miso in a saucepan, slowly whisk in the milk, bring to a boil, then turn off the heat. Put the cornflour in a small bowl, stir in four tablespoons of the hot milk mixture to make a thin paste, then slowly whisk this back into the milk pan. Pop the pan back on a low heat for a few minutes, stirring until the sauce thickens to the consistency of custard, then season with a quarter-teaspoon of salt and turn off the heat.

Putting it all together

To build the lasagne, spread a ladleful of tomato sauce over the base of a 34cm roasting tray, then add a layer of lasagne sheets, followed by, in order, a third of the white sauce, half the spinach, half the sweet potato and half the tomato sauce. Top with another layer of lasagne sheets, then another third of the white sauce, followed by the remaining spinach, sweet potato and tomato sauce. Top with the last of the lasagne sheets and finish with final third of the white sauce.

Scatter the breadcrumbs over the top and bake for 45-50 minutes, until the pasta is tender and the top bubbling and golden brown. Leave to rest for 10 minutes, then serve hot, perhaps with a green salad alongside.