Frosted Chocolate Layer Cake

Instructions

1. Preheat oven to 350 ºF. Coat two 9-inch round or square cake pans with cooking spray; set aside.
2. To make the cake, combine flour, brown sugar, cocoa, baking powder, baking soda and salt in a large bowl. Mix well with a fork to break up brown sugar; set aside.
3. Melt 4 tablespoons of margarine. Combine buttermilk, egg whites, melted margarine and 1 1/2 teaspoons of vanilla extract in a large mixing bowl; using an electric mixer, mix on low speed until blended. Gradually beat in boiling water and then add flour mixture; mix on low speed until blended.
4. Pour batter into prepared pans and bake until a toothpick inserted in the centre comes out clean, about 30 minutes. Cool cakes in pans on a wire rack for 20 minutes; invert cakes onto rack, remove pans and cool completely.
5. Meanwhile, to make the frosting, melt remaining 2 tablespoons of margarine in a small saucepan over medium-low heat. Add milk and chocolate chips; cook until blended and smooth, stirring constantly with a wire whisk, about 3 minutes. Remove from heat, transfer to a large mixing bowl and stir in remaining 1/2 teaspoon of vanilla extract; cover surface with plastic wrap and refrigerate until cool, about 15 minutes. Using an electric mixer on low speed, gradually add powdered sugar and mix until blended.
6. To assemble cake, spread 1/2 cup of frosting on the top of one cake layer. Top with second cake layer and spread remaining frosting over top and sides; slice into 16 pieces and serve.