Peel, wash and chop the carrots. Wash, quarter, seed and finely dice the tomatoes. Peel and chop the onion.
Heat butter. Sauté onion in it. Sauté the flour lightly.
1⁄2 l Stir in water, cream and stock, bring to the boil. Add carrots and simmer sauce for about 5 minutes. Add tomatoes. Season to taste with salt and pepper.
Cut the mozzarella into slices. Layer Maultaschen and vegetable sauce in the mould. Cover with mozzarella and bake in a hot oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer) for approx. 40 minutes.