Cheeseburger-Vegetable Casserole

1 lb ground beef
1/2 cup chopped onion
1/4 cup butter or margarine
1 teaspoon salt
dash of pepper
1 1/2 cups milk
1 1/2 shredded sharp American cheese (6 ounces)
1 teaspoon Worcestershire sauce
1 10-ounce package frozen mixed vegetables
1/4 cup chopped canned pimiento
Package instant mashed potatoes (enough for 4 servings)

In a large bowl crumble the ground beef. Add the chopped onion. Microwave, covered, until meat is brown, stirring several times to break up meat. Drain off excess fat. In a 4 cup glass measure microwave the butter on half power for about 50 seconds. Stir in the flour, salt and pepper. Graduallly stir in the milk. Microwave, uncovered, 1 minute; stir. Microwave until thick and bubbly, about 3 minutes more, stirring every 30 seconds. Stir in 1 cup of  the cheese and the worcestershire sauce. Add meat to the mixture. Turn mixture into a 8x8x2 baking dish. Microwave, covered, 8 minutes turning after 4 minutes.

Prepare the packaged instant mashed potatoes according to package directions except decrease water by 1/4 cup. Spoon the prepred potatoes around the edge of  the casserole. Sprinkle remaining cheese over potatoes. Microwave, uncovered, until cheese is melted, about 1 minute. Serves 4 to 6.