Cook noodles until slightly undercooked, rinse with cold water and separate.
In a saucepan over medium heat, melt butter, add flour and whisk until smooth. Gradually add milk, whisking continuously until thick. Turn off burner and add 1/2 of the grated cheese, salt and pepper.
In a bowl combine ricotta cheese, egg, garlic, 2 cups mozzarella, and parsley. Stir to combine.
Mix shrimp and crab in a bowl.
In a greased 9 x 13 inch pan, layer 1 cup sauce in pan, place 3 noodles side by side, top with ⅓ of the ricotta mixture, top with 1/3 of seafood mixture. Repeat 2 more times topping with remaining sauce, mozzarella and parmesan cheese.
Cover and cook in a 350 degree oven for 30 minutes, uncover and cook for additional 10 minutes or until bubbly and golden on top. Allow to rest for 20 minutes to set.