Preheat oven to 350 degrees F (175 degrees C). Lightly grease one 13x9 inch baking pan.
Cream together 1/3 cup of the cocoa, white sugar, and 1 cup of the butter or margarine until light and fluffy. Add the eggs, and 1 teaspoon of the vanilla and beat well.
Mix flour, baking powder, coconut, and chopped pecans together. Stir flour mixture into the egg mixture and stir until just combined. Pour batter into the prepared pan.
Bake at 350 degrees F (175 degrees C) for 40 to 50 minutes. Smooth marshmallow cream over top of cake while still hot. Let cake cool completely then ice with chocolate icing.
To Make Chocolate Icing: Beat together the confectioner's sugar, the remaining 1/3 cup cocoa, 1 teaspoon vanilla, and 1/2 cup butter or margarine. Continue to beat and add enough evaporated milk to make icing spread on cake.