Heat the fat and sweat the flour in it. Gradually stir in vegetable stock and milk, cook for about 2 minutes. Dice half of the mozzarella and stir into the sauce with Parmesan, cream cheese and 40 g Gouda. Season the sauce with salt and pepper. Cook pasta in boiling salted water according to package instructions until al dente. Wash, clean and halve the tomatoes.
Clean, wash and cut leek into rings. Wash meat, dab dry and cut into cubes. Mix pasta, tomatoes, leek, meat and sauce and fill into a greased casserole dish. Dice remaining mozzarella and sprinkle with remaining Gouda over the casserole. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 30 minutes. Garnish with parsley