Pre-cook the gnocchi in salted water for about 1 - 2 minutes. Drain the water and place the gnocchi in a prepared baking dish. Cut the zucchini and tomatoes into not too thick slices and spread them over the gnocchi in a fan shape.
Now leave out some margarine for the sauce and pour 1 - 2 tablespoons of flour over it. Deglaze with the broth and cream, bring to the boil briefly and then add the herbs. I always take about 2 - 3 tablespoon.
Then spread this sauce over the gnocchi and vegetables. Cut the mozzarella into slices and pour over it. Then bake the gratin for about 20-25 minutes at 180 ° C.