Creamy mushroom lasagne

Method

• step 1

  For the ragu, put the dried porcini mushrooms in a heatproof mug and cover with 125ml boiling water from the kettle. Set aside. Finely chop the chestnut mushrooms or blitz in a food processor to fine pieces.

• step 2

  Heat the oil in a large saucepan or flameproof casserole over a high heat and fry the onions, carrots and chopped chestnut mushrooms with a pinch of salt for 15 mins until the water released by the mushrooms has evaporated, stirring now and then. The mushrooms should be a deep brown colour and the other veg should be soft and slightly coloured.

• step 3

  Add the mixed mushrooms, garlic and most of the thyme, and cook for another 5 mins until the mushrooms have started to soften. Drain the rehydrated porcini, add the soaking liquid to the pan, then finely chop the porcini and add that too. Stir in the wine, passata, ketchup and paprika to combine. Simmer for 25 mins until the ragu has reduced and is thick enough to coat the back of a spoon. Season generously with sea salt flakes and a grinding of black pepper.

• step 4

  Meanwhile, make the béchamel. Melt the butter in a saucepan over a medium heat, then add the bay and cook for a minute. Scatter in the flour and stir until you have a sticky paste. Add the milk in stages, whisking between each addition until you have a thick sauce. Reduce the heat to low and cook for 3-4 mins, stirring occasionally until the sauce is thick enough to coat a spoon. Remove the bay, then mix in the crème fraîche, a generous grating of nutmeg and seasoning.

• step 5

  Heat the oven to 200C/180C fan/gas 6. Rub the olive oil over the base and sides of a large ceramic baking dish (ours was 35 x 20 x 6cm). Arrange a layer of lasagne sheets in the base (you may need to break them so they fit), then spoon over a layer of the mushroom ragu, drizzle with some of the béchamel, and scatter over a handful of the mozzarella. Repeat until you have used all the ragu and the final layer of lasagne sheets, then smooth over a thick layer of béchamel. Sprinkle over the remaining mozzarella and bake for 40-45 mins until the filling is bubbling and the top is golden. Leave to rest for 10 mins, then sprinkle with the remaining thyme leaves before serving.