- 4 tbsp olive oil
- 500g/1lb 2oz sliced fresh porcini or a generous handful of dried porcini
- 2 garlic cloves, sliced
- 150g/5½ oz Parma ham, thinly sliced
- 150g/5½oz butter, plus extra for greasing
- 60g/2¼oz plain flour
- 1.5 litres/2½ pints milk
- 200ml/7fl oz double cream
- 2 tbsp chopped fresh parsley
- 1kg/2lb 4oz fresh pasta dough, rolled out into lasagne sheets
- 400g/14oz Parmesan cheese, grated
- white truffle oil or a fresh truffle
- 100g/3½oz unsalted butter
- salt and freshly ground black pepper, to taste
- Preheat the oven to 180C/160C Fan/Gas 4.
- Heat the olive oil and fry the mushrooms with the garlic for two minutes.
- Add the Parma ham, stir and remove from the heat.
- Cook the butter and flour in a pan over a low heat until it lets off a nutty aroma. Stir in the milk, a little at a time until it is combined and thick.
- Add the double cream and bring to the boil.
- Tip the cooked mushrooms into the sauce, season well with salt and pepper, and add the parsley.
- Butter a 24cm/9½in gratin dish and lay a pasta sheet inside it.
- Spoon over the sauce and add a generous handful of Parmesan cheese. Dot with truffle oil or crumble over a little of the fresh truffle.
- Repeat to make six layers, and finish with more Parmesan and dot with butter.
- Bake in the oven for 25-30 minutes, or until bubbling and golden.