Sausage Potato Lasagna

1/2 bulk sausage
2 cups fresh mushrooms
4 medium potatoes, peeled and thinly sliced
1 10 oz. pkg. chopped spinach, drained
1 1⁄2 cups ricotta cheese
1 egg, beaten
1 medium onion, chopped
2 cloves garlic, minced
2 Tbsp. butter
2 Tbsp. flour
salt and pepper to taste
1⁄2 tsp. nutmeg, optional
1 1⁄2 cups milk
1⁄2 cup parmesan cheese
1 cup shredded mozzarella cheese

Cook sausage and mushrooms, drain and set aside. Place potatoes in pan. Cover with water and bring to a boil. Reduce heat, cover and cook 5 minutes. Drain. In a bowl cook spinach, ricotta and egg. Set aside. In pan sauté onion and garlic in butter until tender. Stir in flour and nutmeg until blended. Add milk and cook 2 minutes. Layer 1⁄2 of potatoes in greased casserole. Top with spinach mixture, then white sauce and 1⁄2 of mozzarella cheese. Then layer the rest. Cover and bake 350° for 35-40 minutes. Sprinkle remaining mozzarella cheese over top and bake uncovered for about 5 minutes. Let stand 15 minutes. Makes 6-8 servings.