Heat oven to 350 degrees. Grease and flour 13x9x2 inch baking pan. In large mixer bowl, combine chocolate, butter and water; with spoon, stir until chocolate is melted and mixture is smooth. Add flour, sugar, sour cream, eggs, baking soda, salt and vanilla; beat on low speed of electric mixer until smooth. Pour batter into prepared pan.
Bake 35 to 40 minutes or until wooden pick inserted in center comes out clean. Cool completely in pan on wire rack. Frost with Quick & Easy chocolate Frosting. dozen to 15 servings.