Chocolate Cake with Sour Cream Frosting

Ingredients

• 2 cups sifted all-purpose flour
• 2/3 cup unsweetened cocoa powder
• 1-1/4 teaspoons baking soda
• 1/4 teaspoon baking powder
• 3 large eggs
• 1-2/3 cups sugar
• 1 teaspoon vanilla extract
• 1 cup reduced-calorie mayonnaise
• 1-1/3 cups cold water
• 12 ounces semisweet chocolate chips
• 1 cup reduced-fat sour cream
• 1/2 teaspoon vanilla extract
• 2 squares (1 ounce each) semisweet chocolate, melted