1/2 cup butter
1 lb fresh mushrooms sliced
3 tbsps fresh lemon juice
8 tsps powdered beef stock base
2 1/2 cups boiling water
1 1/2 cups sour cream
3/4 fresh parsley chopped
Melt butter over low heat in 2-qt saucepan. Add the mushrooms and lemon juice & saute for 8-10 minutes or till tender, stirring frequently.
In a separate bowl combine the beef stock base and water and mix well. Add to mushrooms, mixing well to blend. Remove from heat and let cool about 10 minutes. Slowly blend in the sour cream, stirring to mix thoroughly. (This much can be done 2-3 days in advance and the soup may be held in the refrigerator, tightly covered.)
Shortly before serving the soup, heat over low heat, stirring until hot enough to serve. Do not let the soup come to a boil or the sour cream will separate. Fold in parsley and serve.