Dinner Party Stew

1 lb lean beef chuck, cut into 1-1/2 to 2" cubes
3 medium onions, sliced
1/2 cup tomato juice*
1-3/4 cup beef broth
1 tablespoon sugar
1 small can mushrooms
1/2 cup sour cream

Place all ingredients except sour cream in your slow cooker. Cover and cook on low for 8 to 10 hours. Half an hour before serving, stir in sour cream. *Try substituting a V-8 vegetable juice for tomato juice.