Coat 2 (8-inch) square baking dishes with cooking spray. Combine milk, flour, and nutmeg, stirring with a whisk until smooth. Bring the stock set aside to a boil-over. Gradually add milk mixture to stock mixture, stirring with a whisk. Add the 1 teaspoon of salt. Cook 5 minutes or until thickened, stirring occasionally. Remove pan from heat; stir in grated cheese. Pour 110 grams of sauce into the bottom of each baking dish. Top each with 2 sheets of pasta, 400grams of chicken, 110grams of sauce, and a sprinkle of the shredded mozzarella. Make sure the pasta is covered with the sauce. Repeat layers once with pasta, chicken mixture, and sauce. Top dishes evenly with remaining 4 pasta sheets, remaining 110grams of sauce, and remaining grated mozzarella.