Cut the meat into steaks. Add salt and pepper to taste, pour red wine over everything and let the meat sit for a while so that it absorbs the flavor and aroma.
While the steaks are marinating, heat up a frying pan, grease it with oil. Put the marinated meat on the heated frying pan and fry under a closed lid for 40 minutes on each side.
While the steaks are cooking, make the mushroom sauce. Clean the mushrooms and cut them into wedges. Also cut the onion into quarters and fry the mushrooms with the onion in a heated frying pan with butter until golden brown. Add the cream to the pan and fry for another 5 minutes, then add red wine to the sauce and leave for another 2 minutes to evaporate the alcohol.