1. Preheat oven to 375°.
2. Weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and next 4 ingredients (through bay leaf) in a medium saucepan over medium heat, stirring with a whisk. Cook 8 minutes or until thick and bubbly, stirring frequently. Remove from heat; stir in salt and pepper. Spread 1 cup milk mixture in bottom of an 11 x 7-inch glass or ceramic baking dish coated with cooking spray.
3. Heat a large skillet over medium heat. Add 2 tablespoons water and spinach to pan; cook 2 minutes or until spinach wilts. Drain spinach, pressing until barely moist. Increase heat to medium-high. Remove casings from sausage. Add sausage to pan; cook 4 minutes or until browned, stirring to crumble. Remove sausage from pan. Add shallots and garlic to pan; sauté 2 minutes. Stir in remaining milk mixture, spinach, and cooked sausage. Remove pan from heat.
4. Arrange 2 noodles over milk mixture in baking dish; top with 1/2 cup ricotta and one-third spinach mixture. Repeat layers twice. Sprinkle with mozzarella and Parmesan cheese. Cover with foil coated with cooking spray. Bake at 375° for 40 minutes. Remove foil.
5. Preheat broiler to high.
6. Broil 4 minutes or until cheese is golden brown. Let stand 10 minutes.