Stir cheese into hot white sauce until melted.
Combine cheese sauce and cooked macaroni in 1 1/2 -quart casserole.
Toss lightly to mix.
Microwave 5 minutes on '8', until bubbly, stirring after 3 minutes.
Let stand 3 minutes, covered.
Garnish with parsley, if desired.
For ovens without solid state heat control, Microwave 4 minutes on HIGH, stirring after 2 minutes.