COOK macaroni according to package directions for al dente (slightly undercooked); DRAIN.
GREASE 2 1/2 quart shallow casserole; HEAT oven to 375 degrees.
In a saucepan over medium-high heat, COMBINE flour, mustard, salt, and milk, STIRRING constantly.
REMOVE from heat; STIR in Parmesan, cottage cheese and cheddar; ADD macaroni; MIX.
TRANSFER macaroni mixture to casserole; COVER; BAKE 25 minutes.
UNCOVER; TOP with mozzarella; BAKE for another five minutes.
May substitute reduced fat Jarlsberg or Swiss cheese for Mozzarella.
Per Serving (excluding unknown items): 305 Calories; 15g Fat (38.4% calories from fat); 23g Protein; 30g Carbohydrate; 1g Dietary Fiber; 45mg Cholesterol; 539mg Sodium. Exchanges: 1 1/2 Grain(Starch); 2 1/2 Lean Meat; 1/2 Non-Fat Milk; 1 1/2 Fat.