Cut the jacket potatoes into slices. Brown the onion and leek in a non-stick pan. Add the carrots and diced tomatoes. Season to taste with the spices. Cook for a short time so that the vegetables still bite.
Put half of the potato slices in a greased baking dish, season with rosemary. Spread the vegetables on top and cover with the remaining potatoes.
Make a sweat out of the milk, the vegetable stock and the flour, season with the spices. Spread over the casserole and sprinkle with the grated cheese. Bake the casserole in the oven at 175 ° C for around 20 minutes.