Warm the olive oil in a big saucepan and add the beef medallions until brown (for 3-4 minutes each side). Add a pinch of salt, remove the medallions from the saucepan and keep them warm in the oven. In the saucepan you used to cook the medallions add mascarpone, mustard, coarsely ground green pepper and 3-4 spoons of water. Serve medallions dressing with the mascarpone cream and green salad on the side.