1 med. onion
1 tbsp. butter
1 (4 oz.) can mushrooms, drained
1 pkg. processed American cheese slices
1 firm ripe tomato, peeled & sliced
1/4 c. diced celery
2 c. ground cooked ham
1/4 tsp. dry mustard
1/2 tsp. prepared horseradish
1 (8 oz.) pkg. processed Swiss cheese
1 (9") baked pie shell

Saute onion and celery in butter until soft. Stir in ham, mushrooms, mustard and horseradish. Spoon half the mixture into shells. Top with tomato slices. Cube 4 slices American and 4 slices Swiss cheese. Sprinkle over tomatoes; top with remaining ham mixture. Cut remaining cheese in triangles. Arrange on top of pie. Bake in moderate oven, 350 degrees, about 30 minutes or until ham mixture is heated through and cheese is melted. Serves 6.