Sear the sprouts in a pan with a knob of butter and set aside. Make a béchamel with 100g of melted butter, 100g of flour by drying on the stove, add 700ml of hot milk, salt and perfume with nutmeg. Make a tomato sauce. Grease a baking dish and arrange a first layer of sprouts, cover with the béchamel, mortadella, a little mozzarella and a spoonful of tomato sauce. Continue like this until exhaustion, sprinkling the last surface layer with grated parmesan and a few curls of butter. Place in a preheated oven at 180 degrees for 15 minutes.