Peel the onions and finely dice them. Clean the mushrooms, rub and cut into thin slices or pieces.
Heat the butter in a pan and sauté the onions and mushrooms in it. Pour in the wine and let it boil. Mix in the parsley, creme fraiche and cheese, season with salt and pepper.
Put the mushroom mixture in the pans at the table and bake in a hot raclette maker for 5 - 7 minutes until golden brown.