Beef Stroganoff

1/3 cup butter
1/2 cup finely chopped onions
1/2 pound fresh mushrooms, sliced
1 1/4 pounds top round beef cut in strips
2 Tbsp. flour
1 cup water
1/2 tsp. salt
2 Tbsp. tomato paste
3/4 tsp. Worcestershire sauce
3/4 cup sour cream
1/4 cup heavy cream
1 1/3 cups packaged pre-cooked rice.
1/2 tsp. salt
1 1/2 cups boiling water
2 Tbsp. butter

Melt 4 Tbsp. butter in a saucepan. Add onions and mushrooms and saute until golden brown, remove from heat and set aside. Melt remaining butter in skillet. Roll beef in flour and saute until browned. Add water, 1/2 tsp. salt, onions and mushrooms. Cover and simmer gently until beef is tender (about 1 1/2 hours). Add tomato paste, Worcestershire sauce, sour cream, heavy cream and mushrooms. Heat thoroughly. Meanwhile, add rice and 1/2 tsp. salt to boiling water in saucepan. Mix just to moisten all rice. Cover and remove from heat. Let stand 13 minutes. Add 2 Tbsp. butter and mix lightly with fork. Arrange on platter and top with beef stroganoff.