- Preheat oven to 350°F (180°C).
- In large saucepan, cook macaroni according to package directions; drain. In large saucepan, melt 4 tbsp (60 mL) of the butter. Sauté onion until tender. Blend in flour and dry mustard. Gradually stir in milk. Cook and stir over medium heat until mixture boils and thickens.
- Remove from heat. Add cheddar, swiss and mozzarella and stir until cheeses are melted. Return to low heat if necessary to melt all of the cheese. Fold in macaroni and parsley. Add salt and pepper to taste. Spoon mixture into 2 qt. (2L) shallow rectangular casserole.
- Melt remaining 1 tbsp (15 mL) butter; toss with breadcrumbs. Sprinkle over casserole. Bake 20 minutes or until heated through.
- Excellent source of folate and calcium.