Wash and clean porcini and chanterelles. Mushrooms wash and clean. Cut the porcini into slices. Cut chanterelles and mushrooms in half if necessary. Peel and finely chop the onion.
Wash the thyme, shake dry and, except for something to garnish, pluck leaves from the stalks. Heat 2 tablespoons of oil in a large pan. Fry the rump steaks for about 3 minutes on each side. Season with salt and pepper.
In the meantime, heat 2 tablespoons of oil in a second pan. Sauté the mushrooms in it, season with salt and pepper. Add the onion and thyme leaves and fry briefly. Stir in sour cream and bring everything to the boil once.
Season to taste with salt and pepper. Arrange the steaks with the mushroom cream on plates. Garnish with thyme. Baguette tastes good with it.