Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch baking pan.
In a medium saucepan over medium heat, melt the butter and stir in the cocoa powder until smooth. Remove from heat and stir in the sugar, eggs, and vanilla. Mix in the flour, baking powder, and salt. Fold in the chopped pecans and chocolate chips. Spread evenly into the prepared pan.
Bake for 25 minutes in the preheated oven. Do not overbake. Cool in pan.
To make the frosting, combine the condensed milk and chocolate chips in a medium saucepan over medium heat and stir until melted and smooth. Spread over cake.
Interesting Facts
This cake is also known as Mississippi Mud Pie.
This cake is traditionally served cold.
This cake is best served with freshly whipped cream.