Lasagna rolls with ham and mushrooms

Preparation
Remove the stems from the mushrooms, dry them and chop them finely. Cook them in a pan with a knob of butter, salt and pepper, until they no longer release water.
Prepare the béchamel by melting the butter in a saucepan, adding the flour, whisking for 20 seconds and then gradually adding the 40 cl of milk. Blend until thickened between additions of milk. Take 100 g and set it aside, salt and pepper the rest and add the parmesan, then the mushrooms and 1 tablespoon of parsley sprigs, mix.
Cut the lasagne in 2, cover them with a spoonful of mushroom béchamel sauce, spread them well, then add the slice of ham and another spoonful of béchamel sauce, roll up and place in the baking dish.
Repeat the operation for the 10 slices, add the remaining 10 cl of milk to the béchamel and cover the lasagne with it.
Rolled lasagna with ham and mushrooms
Sprinkle with the remaining parmesan and bake for 25-30 minutes at 180°C (depending on the oven).
During cooking, sprinkle the bottom of the baking dish with the more liquid bechamel.