Method

1. Preheat the oven to 240C/220C Fan/Gas 9.

2. Put the chestnut and oyster mushrooms into a food processor in three or four batches and pulse each batch until finely chopped (or finely chop everything by hand). Toss the chopped mushrooms in a large bowl with 3 tablespoons of oil and 1 teaspoon of salt.

3. Line a 40x35cm/16x14in baking tray with baking paper and spread out the mushroom mixture on the tray. Bake for 30 minutes near the top of the oven, stirring three times during cooking, until the mushrooms are golden brown. They will have reduced in volume significantly. Set aside.

4. Meanwhile, combine the dried mushrooms, chillies and stock in a large bowl and set aside to soak for 30 minutes. Strain the liquid into another bowl, squeezing as much liquid from the mushrooms as possible to get about 340ml/11fl oz. If you have any less, top up with water. Very roughly chop the rehydrated mushrooms (you want some chunks) and finely chop the chillies. Set the stock and mushroom mixture aside separately.

5. Put the onion, garlic and carrot in a food processor and pulse until finely chopped (or finely chop everything by hand). Heat 4 tablespoons of oil in a large casserole over a medium–high heat. Once hot, add the onion mixture and fry for 8 minutes, stirring occasionally, until soft and golden.

6. Pulse the tomatoes in the food processor until finely chopped (or finely chop by hand), then add to the pan along with the tomato purée, 1½ teaspoons of salt and 1¾ teaspoons of black pepper. Cook for 7 minutes, stirring occasionally. Add the rehydrated mushrooms and chillies and the roasted mushrooms and cook for 9 minutes, resisting the urge to stir: you want the mushrooms to be slightly crisp and browned on the bottom. Stir in the reserved stock and 800ml/1½ pint of water and, once simmering, reduce the heat to medium and cook for about 25 minutes, stirring occasionally, until you get the consistency of a ragù. Stir in 100ml/3½fl oz of the cream and simmer for another 2 minutes, then remove from the heat.

7. Preheat the oven to 220C/200C Fan/Gas 7. Combine both cheeses and both herbs in a small bowl.

8. To assemble the lasagne, spread one-fifth of the tomato sauce in the bottom of a round 28cm/11in baking dish (or a 30x20cm/12x8in rectangular dish). Top with one-fifth of the cheese mixture, followed by a layer of lasagne sheets, broken to fit where necessary. Repeat these layers three more times in that order, and finish with a final layer of sauce and cheese. You will have five layers of sauce and cheese and four layers of pasta.

9. Drizzle over 1 tablespoon of cream and 1 tablespoon of oil, then cover with foil and bake for 15 minutes. Remove the foil, increase the temperature to 240C/220C Fan/Gas 9 and bake for another 12 minutes, turning the dish round halfway. Turn the oven to the grill setting and grill for a final 2 minutes, until the edges are brown and crisp. Set aside to cool for 5 or so minutes, then drizzle over the remaining tablespoon of cream and oil. Sprinkle over the remaining parsley, finish with a good grind of pepper and serve.