Tasty Macaroni Cheese

Ingredients
6 teaspoons (30g) margarine
6 teaspoons plain flour
1/2 teaspoon each powdered mustard and salt
1/8 teaspoon pepper
1 1/2 cups liquid skim milk
330grams tasty grated cheese
3 cups cooked macaroni
1 medium tomato, sliced
30 grams grated parmesan cheese

Method
In 2 litre casserole add margarine; microwave on high until melted, 40-50 seconds. Blend in flour, mustard, salt and pepper. Using wire whisk or a fork, gradually stir in milk, mixing well. Microwave milk mixture on high until thickened, 7-10 minutes, stirring 4 times during process. Add tasty cheese, stirring until melted. Add macaroni and stir to combine.
Put mix in 21×21x4 casserole dish that has been sprayed with non-stick spray. Put tomato and parmesan on top. Microwave on high 4-5 minutes. Place under grill until lightly browned if necessary.