Clean the mushrooms and unscrew the stalk. Finely dice the mushroom stems. Wash and clean the tomatoes and cut off the lids. Hollow out the tomatoes. Cut ham into small cubes. Wash parsley, dab dry and cut into fine strips.
Mix ricotta and egg yolk. Fold in diced ham, mushrooms and parsley. Season with salt, pepper and oregano. Cut tomato lids into small cubes. Fill tomatoes and mushrooms with the ricotta cream.
Spread cheese and pine nuts on top. Place the mushrooms and tomatoes in a greased casserole dish. Add tomato cubes and stock. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 20 minutes.
It goes well with bread.