This is an updated recipe from a couple of years ago. While the previous incarnation was as delicious as I had described it, I felt it could be stepped up a little to incorporate more intensity and richness. I do love mushrooms so getting all the mushroom flavour to be its best is key. This recipe finally elevates this simple and quite humble dish into something really special. A must try.
For the bechamel sauce:
4 tablespoons plain flour
1 litre milk
1/2 teaspoon grated nutmeg
40g grated parmesan
40g grated cheddar cheese
Salt & pepper
For the lasagne:
1kg button mushrooms (thinly sliced)
25g dried porcini mushrooms (soaked in 300ml hot water)
3-4 tablespoons olive oil
1 onion (finely chopped)
3 cloves garlic (finely chopped)
1 celery stalk (finely chopped)
Salt & Pepper
2 tablespoons fresh rosemary (finely chopped)
2 tablespoons fresh sage
Pack of dried lasagne sheets
4 tablespoons truffle pecorino (grated) mixed with 2 tablespoons parmesan cheese (grated) (or just 6 tablespoons parmesan)
Preheat oven to 180ºC
To make the sauce:
In a saucepan, melt the butter then stir in the flour. Cook for 1-2 minutes then pour in the cream and milk, whisking constantly. Add the nutmeg, salt and pepper and whisk until the consistency of double cream (about 3-4 minutes). Remove from the heat and stir in the parmesan and cheddar until melted then set aside.
Drain the porcini mushrooms, keeping the liquid. Chop the mushrooms and set aside.
Heat the olive oil in a large frying pan over a moderate heat. Add the onion, garlic and celery and fry gently for 4 minutes until soft and translucent. Add the rosemary, sage and both the button and porcini mushrooms and fry for about 10 minutes, until most of the water from the mushrooms has evaporated. Stir in about 1/3 of the béchamel sauce along with the soaking liquid from the porcini mushrooms. Let this simmer for 3-4 minutes until rich and creamy. Remove from the heat and set aside.
In a rectangular casserole dish, spoon a thin layer of the mushroom mix over the base. Add a sheet of lasagne, then a light sprinkling of truffle pecorino and parmesan and finally a few spoons of the béchamel sauce. Repeat the process three or four times, ending with a layer of mushrooms with the remaining bechamel sauce spread over. Sprinkle the top with the remaining pecorino and parmesan. Bake in the oven for 25 minutes. Increase the heat to 220ºC and bake for another 8-10 minutes to brown the top.
Remove from the oven and cool slightly for 10 minutes before serving.
Serve with a simple rocket and tomato salad.