Mushrooms cut into thin slices, chop the onion. Sliced mushrooms fry in vegetable oil or butter 5 minutes, add the onion and fry for another 5 minutes. In a saucepan, not boiling, heat the cream, add the mushrooms with onions, salt and pepper and gently warm everything together. If sour liquid, it is first necessary to connect it (still cold), 1 tablespoon of flour, dried on a dry pan. Hot mixture of mushrooms and onions in sour cream to spread in ramekins or small molds for baking, sprinkle with grated cheese. Put in the preheated oven until complete dissolution of cheese and browned.