Peanut Butter Fudge Cake

2 c. all-purpose flour

2 c. sugar

1 tsp. baking soda

1 c. margarine

1/4 c. cocoa

1 c. water

1/2 c. buttermilk (1/2 c. milk plus 1/2 Tbsp. lemon juice--let stand for 5 minutes)

2 large eggs, slightly beaten

1 tsp. vanilla extract

1 1/2 c. creamy peanut butter

Chocolate frosting (see recipe below)

Preheat oven to 350.  Combine flour, sugar, and baking soda in a large mixing bowl and set aside.  Melt margarine in a heavy saucepan; stir in cocoa.  Add water, buttermilk, and eggs, stirring well.  Cook over medium heat stirring constantly until mixture boils.  Add to flour mixture; stir until smooth.  Stir in vanilla extract.  Pour batter into a greased, floured 13x9 baking dish.  Bake for 20-25 minutes or until a toothpick inserted in the center comes out clean.  Set pan on a wire rack.  Cool for 10 minutes.  Spread peanut butter on warm cake.  Cool completely for 30 minutes, then spread chocolate frosting on top of peanut butter. 

Chocolate frosting:

1 lb. powdered sugar (4 1/2 cups)

1/2 c. margarine

1/3 c. buttermilk (1/3 c. plus 1/3 Tbsp. lemon juice--let stand for 5 minutes)

1/4 c. cocoa

1 tsp. vanilla extract

Put powdered sugar in a large bowl.  Bring margarine, buttermilk and cocoa to a boil in a saucepan over medium heat; stir constantly.  Pour cocoa mix over sugar, stirring until smooth.  Mix in vanilla extract.