For the marble wafers, first sift flour and baking powder.
Cream butter with sugar and salt. Gradually beat in the eggs. Alternately add flour mixture and milk and mix well. Pour 1/3 of the batter into another bowl and stir in the cocoa powder. Let rest for about 10 minutes before using.
In a greased, heated waffle iron, first add some of the light batter and then a little of the dark batter. Bake the marble waffles until crispy.