Ground Beef Patties with Cheese Sauce

1 1/2 Lb. lean ground beef

1 Small onion -- chopped

1 Tsp. salt

1/4 Tsp. pepper

1 Tbsp. minced parsley

2 eggs

Sauce: 2 Tbsp. butter

2 Tbsp. flour

1 C. milk

1 Tsp. Dijon mustard

1/2 Tsp. salt

34 C. diced Swiss or Cheddar

cheese 1 fresh tomato -- chopped

Mix all and divide and shape into 4 patties. Place in a baking dish. Bake at 400 degrees for 20 to 25 minutes, or until meat is done to your liking. While meat bakes, prepare sauce.

Sauce: Melt butter in a small saucepan; add flour. Over high heat, stir in milk; heat and stir constantly until thick. Stir in mustard, cheese and salt; stir until cheese is melted. Add tomato. Pour sauce over cooked meat patties. Top with a slice of cheese and a slice of tomato. Return to oven just long enough to heat tomato and melt the cheese, 3 to 5 minutes.