Heat oven to 350 F. Line 3 12-hole muffin tins with cupcake liners. Melt the butter in a small saucepan over low heat on the stove, or in a small glass bowl in the microwave. Remove from heat and let cool completely.
In a large bowl, combine 1 1/4 cups cocoa, 2 1/2 cups flour, 2 1/2 cups sugar, 2 1/2 teaspoons baking soda, 1 1/4 teaspoons baking powder and 1 1/4 teaspoon salt with a mixing spoon. Separate one of the eggs, keeping the egg yolk for this recipe.