Peel and halve the onion and cut into fine slices. Clean the fresh mushrooms and cut into fine slices.
Heat the oil in a deep pan. Turn the schnitzel in flour, knock off and fry all over. Then add the onions and mushrooms and fry them too. Then add the white wine and let it boil down, possibly adding a little salt and pepper. When the white wine is mostly overcooked, add the cream, add salt and pepper, sprinkle in about a pinch of garlic powder or less and the vegetable stock, add parsley. Simmer on medium heat for about 5-10 minutes until the sauce has thickened a little.
Spätzle or rice and a simple green salad are good side dishes.