Preheat oven to 350 degrees F. Spray an 11 x 17 inch baking pan with no stick cooking spray.

To prepare chocolate cake: Mix butter, oil, cocoa, and water together in a large saucepan. Bring to a boil. Remove from heat. Beat in the sugar and flour with an electric mixer. Whisk together the buttermilk, soda, egg, and vanilla. Beat into cake batter until well combined. Pour into baking pan.

Prepare the peanut butter cake by placing peanut butter, oil, butter, and water into a large saucepan. Bring to a boil and then remove from the heat. Beat in sugar, flour, milk, egg, baking soda, and vanilla. Mix until well combined . Spoon or pour over the chocolate cake layer.

Bake about 20 minutes, or until toothpick inserted into the center comes out clean.

Prepare the chocolate frosting by placing the butter, milk, and cocoa into a medium size saucepan. Heat until it starts to boil, then remove from the heat. Beat in the confectioner sugar and vanilla with an electric mixer, until smooth. If frosting becomes too thick, add a few drops of milk at a time. Pour and spread the icing over cake while still warm.

Allow icing to harden on the cake before preparing the peanut butter frosting.

For the peanut butter frosting, Place the peanut butter, milk, and butter in a medium saucepan. Bring to a boil and then remove from heat. Beat in the confectioner sugar. Stir in the pecans. If frosting becomes too thick, may add small amount of milk. Pour and spread frosting over the chocolate frosting,

Allow cake to cool completely and cut into desired size squares.