1 Bake white cake mix according to package directions for one 9×13 inch cake. Using the handle of a wooden spoon, poke holes down through the warm cake to the bottom of the pan. Holes should be at approximately 1 inch intervals.
2 In a large saucepan over low heat, melt the butter with the water. Stir in the chocolate chips, mixing constantly until they are melted. Mix in the peanut butter, and stir until smooth. Remove from heat.
3 Pour the warm chocolate peanut butter mixture over the cake, smoothing the surface and gently pressing it into the poked holes. Refrigerate for 3 hours before serving.