Preheat oven to 350. Line baking sheets with parchment paper.
Whisk together the flour,cocoa, espresso powder and salt; set aside.
Cream together the butter and sugar until light an fluffy. Beat in the egg and vanilla until well combined.
In 3 additions, add the flour mixture at low speed. Scrape down sides and bottom of bowl as needed.
Roll the dough on a lightly floured and cocoa-ed surface. (I mixed the 2 of these, then spread on my rolling surface, on my rolling pin, and used it to dip my cookie cutters.)
Cut the cookies with a square cutter, then divide into smaller squares, if necessary, using a bench scraper.
Freeze cut cookies five minutes.
Bake 8 minutes. Let cool completely.
With white royal icing and a #4 (or so) plain tip, pipe the x’s and o’s.
With red icing and a #3 or #4 tip, pipe hearts on some of the cookies.
Let the icing dry (overnight is fine).
Mix equal parts meringue powder and water. Brush onto piped designs with a small paintbrush and sprinkle on sanding sugar. Shake off the excess.