Preheat oven to 375 degrees F.
In a casserole, place 1 layer of mushrooms and leeks. Sprinkle with salt, pepper, and parsley. Cover with 2 ounces of butter and cream. Repeat process three more times and cover with bread crumbs. Bake until mushrooms are tender and crust is golden brown, about 20 minutes
Recipe courtesy of Michael Symon