2 tablespoons oil
2 tablespoons butter
1 medium onion, chopped
2 pounds lean ground beef
2 eggs
2 teaspoons salt
1/2 teaspoon pepper
1/4 teaspoon tarragon
1/4 teaspoon marjoram
3 tablespoons flour
5 tablespoons tomato paste
3/4 cup beef stock
1 tablespoon Worcestershire sauce
2 teaspoons vinegar
1/2 pound mushrooms, sliced
1 cup sour cream

Saute onion in a large skillet in 1 tablespoon oil and 1 tablespoon butter until golden brown. Put the onion in the slow cooker.
Mix together the beef, eggs, salt and pepper. Form into small meatballs.

Brown meatballs in same skillet.

Sprinkle meatballs with the tarragon, marjoram and flour. Shake the frypan to turn the meat balls and coat them with the flour. Put into slow cooker.

Combine tomato paste, beef stock, Worcestershire sauce and vinegar in the skillet. Scrape the bottom of the pan and cook for two minutes. Pour over meatballs.

Cover and cook on low for about 2 1/2 hours.

Heat remaining butter and oil in skillet and saute mushrooms until tender.

Add the mushrooms and the sour cream to the meatballs and continue cooking until heated through. Serves 8 to 10.