Created by ForeverMama on July 26, 2016
Step 1: Cook noodles according to package directions, drain well, and set aside.
Step 2: Coat a large skillet with cooking spray; add sausage, and cook over medium-high heat until sausage is browned, stirring often. Add onion; cook 2 minutes, stirring often.
Step 3: Stir in apple; remove from heat, and set aside.
Step 4: Melt 3 tablespoons butter in a heavy saucepan over low heat; add flour, stirring until smooth. Cook stirring constantly, until thickened and bubbly. Stir in mustard and next 3 ingredients.
Step 5: Layer half of cooked noodles in a greased 13" x 9" x 2" baking dish. Spoon sausage mixture over noodles; sprinkle 1 cup Swiss cheese over sausage mixture. Top with remaining noodles. Pour sauce over noodles. (if desired, cover and chill overnight. Let stand at room temperature 30 minutes before baking.)
Step 6: Cover and bake at 350-degrees-Fahrenheit for 45 minutes or until thoroughly heated.
Step 7: Uncover and sprinkle with remaining 1 cup Swiss cheese.
Step 8: Combine bread crumbs and 2 tablespoons butter; sprinkle over casserole.
Step 9: Bake 10 more minutes or until sheese melts and breadcrumbs are browned.
Step 10: Serve immediately.