Clean and clean the mushrooms and cut them into strips. Peel and finely chop the onion. Wash the meat and dab dry. Heat oil in a coated pan. Fry the meat for 3-4 minutes on each side, season with salt and pepper.
Remove the meat, wrap it in aluminium foil and let it rest for a short time. Add mushrooms, onion and peppercorns to the pan. Fry for approx. 5 minutes, turning. Season with salt. Add cream and bring to the boil.
Arrange steak and mushroom sauce, sprinkle with coloured pepper and garnish with rosemary.