Clean and wash the mushrooms and, depending on size, cut them in half or quarters. Peel and halve onions and cut them into strips. Wash the thyme and remove the leaves. Wash the meat, dab dry and season with salt and pepper.
Heat 1 tablespoon of oil in a frying pan. Fry the meat for 2-3 minutes on each side, season and remove. Heat 2 tablespoons of oil in a frying pan. Sauté the mushrooms well in it. Add onions and fry for 1-2 minutes.
Dust the mushrooms and onions with flour and sauté briefly. 1⁄4 l Stir in water, cream and stock, bring to the boil. Season to taste with salt and pepper. Add thyme and meat. Cover and let it stew for about 5 minutes.
Put slices of bread on plates. Take the fillets out of the sauce, cut them open and spread them on the breads. Pour the sauce evenly over them and serve immediately.