Peel and slice the potatoes. Wash and clean the tomatoes, leeks and onions and also cut into slices or rings.
Layer half of the potato slices in a baking dish, then layer the tomatoes, leek and onion as well as the spices in the dish and finally place the rest of the potatoes on top. Spread the grated cheese on the potatoes and pour the cream over them.
Bake in a preheated oven at 200 ° C for approx. 1 - 1.5 hours, depending on the type of potato (if necessary, place baking paper over the casserole, then the cheese will not turn too brown).