Boil the potatoes until half done and sauté the cleaned and sliced mushrooms in a little oil. Season them to taste with some of the spices.
In a greased baking dish, arrange a row of potatoes, sprinkle with a little salt and pepper, a little oil and arrange a row of mushrooms. Repeat in this order until out of products.
Beat all the ingredients for the topping, pour them over the dish and put it to bake in a moderately hot oven until nice and browned.