Onions peel, finely dice. Clean the mushrooms, wash if necessary. Heat the fat in a large pan (or 2 pans). Fry the onions in it until transparent. Add the mushrooms and fry over high heat for about 10 minutes
Add peas, season. Boil up with 3/8 l water, cream and possibly wine. Simmer for about 5 minutes.
Dice the cheese. Melt in the sauce while stirring. Thicken sauce, season to taste. Serve everything with ham. Serve with: farmhouse bread