Beat together butter and sugar. Add egg and molasses and beat until smooth. Combine flour, cocoa, baking soda, ginger, pepper and cinnamon in another bowl. Stir into butter mixture. Divide dough in half. Wrap in plastic and refrigerate for 2 hours.
Heat oven to 350° F. Roll half of dough on a floured surface to 1/8 inch thick. Cut circles with a 3 1/2-inch cutter; transfer to ungreased baking sheets. Reroll scraps; cut. Repeat with the remaining dough.
Bake at 350° F for 11 minutes. Transfer to wire racks to cool. Spread with Royal Icing; decorate with candy corn and mini chips to resemble a face.
In a medium-size bowl, combine confectioners' sugar, powdered egg whites and 2 tablespoons cool water. Beat on high with an electric mixer for 5 minutes, adding more water as needed.