Mix the milk and vegetable stock and bring to the boil. Stir in the polenta, stirring constantly. Keep stirring until a solid mass has formed, then remove from the heat and stir in the margarine. Season to taste with salt, pepper, nutmeg and herbs of Provence.
Slice the tomatoes and mozzarella, and dice the zucchini.
Place half of the tomato slices and about half a ball of mozzarella in a greased baking dish. Then spread the polenta mixture over it up to about 4 tablespoon.
Stir the zucchini into the rest of the polenta. Now place the remaining tomato slices in the tin, spread the polenta and zucchini mixture over it and then top with mozzarella.
Bake at 200 ° C for about 15 minutes.
Tip: If you prefer less liquid, you can use less water for the polenta, bake longer or let the finished casserole evaporate a little.