Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9×13 inch pan.
In a saucepan, combine 1 cup margarine, 1/4 cup cocoa, water, eggs, and 1/2 cup buttermilk in a saucepan. Cook, stirring occasionally, until it bubbles. Remove from heat and set aside.
In a large bowl, mix flour, 2 cups sugar and baking soda. Make a well in the center and pour in chocolate mixture. Add vanilla and beat until smooth. Spread batter into prepared pan.
Bake in the preheated oven for 25 to 30 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow to cool.
In a small bowl, mix peanut butter and oil. Spread over top of cake. In a saucepan, combine 1/4 cup cocoa, 1/2 cup margarine, and 6 tablespoons buttermilk. Heat until boiling. Remove from heat and stir in vanilla. Place confectioners’ sugar in a large bowl. Beat in chocolate mixture and continue mixing until smooth. Spread over cake.
Source: Read Full Article