Soak rolls in cold water. Clean and halve the mushrooms. Heat the fat in a pan and fry the mushrooms vigorously for 5-6 minutes. Season with salt and pepper, put them on a plate and let them cool down.
Wash the tomatoes, dab dry and cut into cubes. Drain the mozzarella and also cut into cubes. Peel onions and garlic. Finely dice onions, press garlic through a garlic press.
Squeeze the bread well and knead with minced meat, eggs, onions, garlic, tomato paste, dried oregano, a little salt and pepper. Knead about 3/4 of each of the mushrooms, tomatoes and mozzarella under the minced dough and form a roll of about 40 cm.
Grease a grease pan with a little oil and place the roll diagonally inside. Bake in a preheated oven (electric: 200 °C/ gas: level 3) for 30-40 minutes. Then sprinkle the roll with 50 g Gouda and cover with the remaining tomatoes, mushrooms and mozzarella.
Sprinkle with the rest of the Gouda and fry for 20-30 minutes. Cut the chopped roll into about 20 slices and arrange on a plate. Garnish with fresh oregano and serve hot or cold.
Tomato sauce, for example sun-dried tomato sauce, tastes good with it.