Lightly oil a baking dish. Spread half of the potatoes on the bottom, and arrange the mushrooms over top. Add half of the cream and spices over them. Sprinkle some breadcrumbs and cheese over them.
Spread the remaining potatoes over top, and pour the remaining cream over everything. Sprinkle on some more breadcrumbs.
Bake for 20 minutes. Add some more cheese on top, then return to the oven to melt and brown the cheese.