Clean and wash the mushrooms. Cut out stems and chop finely. Peel and finely chop the onions. Wash the thyme, dab dry and chop, except for a little to garnish.
Clean, wash and finely dice the peppers. Heat the oil in a pan. Fry the onions in it until transparent. Add chopped mushroom stems, paprika and thyme. Cook for about 2 minutes. Season well with salt and pepper.
Add the filling to the mushrooms. Place in greased aluminium foil. Grill for about 10-15 minutes. Serve garnished with thyme. Serve with a salad of paprika and pickled peppers and fresh baguette.