Meat balls with sour cream

2 lbs. ground beef
1/2 teaspoon tarragon
2/3 cup milk
salt and pepper to taste
4 slices bread
1 large onion
1/4 cup margarine
2 eggs separated
1 tablespoon dill

1. Cut off the crust and place bread in a small bowl and add milk. Mince the onion and add it to a large skillet. Saute onion in the margarine until soft. Combine in a large bowl the ground beef the beaten egg yolks bread mixture, onion, dill, tarragon, salt and pepper.
2. Beat the egg whites to soft peaks, fold into the beef mixture. Form small balls from the beef mixture and sprinkle with flour.
3. Brown the meat balls in a skillet, add a 1/4 cup of margarine over medium heat. In a another skillet saute 1/2 lb of mushrooms in 3 tablespoons of margarine until browned. Add the meat balls and stir in 1 1/2 cups of sour cream covering the meat balls and simmer in the mixture over low heat for 30 minutes. Stir occasionally. Salt and pepper to taste.