Use Halloween-themed cookie cutters, like pumpkins and ghosts, and colored sugars or icing to turn this simple cookie recipe into a festive holiday activity.
Cream together the butter and sugar in a bowl. Add the egg and then the second yolk, stirring just to combine. Sift flour, cocoa and salt together and then add to the bowl, a little at a time, mixing until dough is evenly combined. Roll dough out to approximately ¼-inch thickness between 2 pieces of parchment paper. Place in the refrigerator until cold, about 30 minutes.
Preheat oven to 375°F. Line a cookie sheet with a Silpat® or parchment paper. Using cookie cutters, cut dough into desired shapes. Sprinkle cookies with sugar and bake until dry to the touch, about 7-8 minutes. Let cool.