Preparation: In a bowl dissolve butter together with two tablespoons of oil, joined the onion and crushed scalogno, brown well and add mushrooms, cut into slices, salt, pepper and add the juice of a lemon. Cook until the water produced by mushrooms will absorbed. Now add the cream, a little of butter. Form with the previously thawed puff pastry of thin discs in which put 2 spoonfuls of sauce with mushrooms with 2 tablespoonfuls of grated cheese. Close well the edges forming half-moons. Put these Dartois in a plaque for previously dampened oven and cook at high heat for 20 minutes.