Clean the mushrooms and cut them in slices. Roughly dice the onions.
Put the mushrooms in a large deep pan and sauté in a little oil with the lid closed. Onions with it. Salt and pepper. Steam until the liquid has evaporated. Deglaze with milk and cream. Add the crème fraîche. Add parsley and stock powder. Season again with salt and pepper and bind with the starch.
Excellent breaded schnitzel and croquettes or pork fillet medallions go well with it.