Lasagna Chicken Florentine

1-1/2 tablespoons butter or stick margarine
3 tablespoons all purpose flour
2 12 ounce cans evaporated skim milk
1/2 teaspoon salt
1/8 teaspoon ground nutmeg
cooking spray
6 no boil lasagna noodles
1 1/2 cups shredded cooked chicken breast
1 10 ounce package frozen chopped spinach, thawed, drained and squeezed dry
1/2 teaspoon freshly ground black pepper, divided
3/4 cup preshredded reduced fat pizza blend cheese or cheddar cheese

Preheat oven to 450F. Melt butter in a medium saucepan over medium heat. Add flour; cook 30 seconds, stirring constantly. Gradually add milk, stirring with a whisk until blended. Stir in salt and nutmeg; cook until thick, stirring constantly about 3 minutes. Spread 1/2 cup sauce in bottom of an 8 inch square baking dish coated with cooking spray. Arrange 2 noodles over sauce; top with half of chicken and half of spinach. Sprinkle with 1/4 teaspoon pepper; top with 3/4 cup sauce. Repeat layers, ending with noodles. Spread remaining sauce over noodles. Cover and bake at 450F for 25 minutes or until noodles are tender and sauce is bubbly. Uncover and top with cheese; bake an additional 5 minutes. Let stand 5 minutes.