Finely dice the bacon. Rub the mushrooms with kitchen paper and cut into slices. Cut the spring onions into rings. Leave the bacon on a low heat. Add the mushrooms and stew for four minutes, then leave to cool a little. Chop parsley, grate cheese. Stir in the parsley, cheese and creme fraiche to the mushrooms. Salt and pepper the pork medallions and fry in hot oil for 2 minutes on each side. Grease the ovenproof dish and place the pork medallions in it. Distribute the mushroom mixture evenly on the pieces of meat. Put in the preheated oven, bake to 200 degrees for about 20-30 minutes.