Cut out the stems from the mushrooms and put them aside. Carefully rub the mushrooms with kitchen paper. Finely dice the ham. Clean, wash and dice the peppers.
Wash parsley, dab dry and chop finely. Mix cream cheese, ham, paprika, parsley and egg yolk. Season with salt and pepper. Pour the cheese mixture into the mushrooms. Put the rest of the filling aside.
Cut the mushroom stems into small cubes. Clean and wash the leek and cut into fine rings. Peel and chop onion. Heat oil in a pan. Fry mushroom stems and onion in it. Add leek and deglaze with broth.
Put the vegetables and the rest of the filling in a large ovenproof dish. Place the mushrooms on top. Cook in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 20 minutes. Remove the mushrooms and sprinkle with parsley and garnish.