In a large bowl, sift together the flour, cocoa powder, baking powder and salt. Set the mixture aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugar until light and fluffy, about 3 minutes.
Add the eggs one at a time, beating between each addition, then add the vanilla extract and continue beating, scraping down the sides of the bowl as needed.
Add the flour mixture and beat until the dough is smooth. Divide the dough in half then roll each half in between two sheets of parchment paper or wax paper until they are about 1/4-inch thick. Slide the sheets of dough onto baking sheets (with the parchment paper) and refrigerate them for a minimum of 2 hours and up to overnight. (The refrigeration prevents the dough from spreading when baked, so don’t skip this step!)
Once chilled, preheat the oven to 350°F and line 2 baking sheets with parchment paper. Remove the sheets of dough from the fridge and use a football cookie cutter to cut out shapes. (Alternatively, use a sharp knife to trace out the football shape.) Re-roll the remaining dough and continue cutting until all is used. Repeat with 2nd piece of dough. Arrange the cutout cookies about 2 inches apart on the baking sheets. Bake for 10 to 12 minutes until they are firm around the edges. Remove the cookies from the oven and let them cool for 5 minutes on the baking sheets until you transfer them to a rack to cool completely before decorating.
Decorate: Prepare cookie icing. Spoon or pour the icing into a piping bag fitted with piping tip #2. Pipe the laces/stitching onto each cookie. (Alternately, use a sealable plastic bag and snip the tip then pipe accordingly.) Cookie icing dries to a semi-firm finish in about 10 minutes, but for fully hardened icing, give the cookies up to 24 hours. Once the icing has set, stack the cookies with parchment paper between layers to avoid smudging. Store in an airtight container at room temperature for up to a week.