2 lbs. ground beef
1 lg. egg, slightly beaten
8 thin slices boiled ham
8 thin slices Swiss cheese
2 tbsp. butter
1/2 lb. fresh mushrooms, thinly sliced
1 c. mayonnaise
2 tbsp. tarragon wine vinegar
1 tbsp. parsley, minced
1 tbsp. finely chopped chives
1 tsp. tarragon
8 onion rolls

Combine ground beef and egg. Divide into 16 portions and form thin patties. On eight patties lay ham and cheese, trimmed to fit inside patty, leaving 1/2 inch border. Cook mushrooms and put on. Cover and pinch. Flatten and refrigerate, covered. Mix mayonnaise, vinegar, parsley, chives and tarragon. Refrigerate. Cook and put on sauce.