Wash the schnitzel, pat dry, season with salt and pepper and turn in flour. Fry the schnitzel in oil and layer in a baking dish. Peel the onions, cut into rings and sauté in oil. Clean the mushrooms and cut into slices, sauté as well. Dice the ham and add to the onions and mushrooms. Pour the mixture over the schnitzel, pour the whipped cream on top, leave to stand in the refrigerator overnight.