Gradually add water to unsweetened cocoa. Stir or beat well until mixed.
Whisk together flour, baking soda and salt to combine well. Add sugar, butter or shortening, eggs and 1/4 cup buttermilk to the dry ingredients. Beat for 3 minutes.
Stir in vanilla, remaining buttermilk and cocoa mixture. Beat for another 2 minutes.
Pour batter into a well greased 10" skillet (cast iron is best). Batter should not fill pan more than 2/3 full.
Place candy bar squares (or break up bar) evenly over the top of batter. Cover pan with foil and bake in a 350°F oven for 50-60 minutes.
Serve warm or cold with whipped cream or ice cream.
Submitted by: CM