Preheat oven to 350º
Cream butter, sugar, and peppermint extract until smooth
Add cocoa powder and flour, and mix until dough comes together
Roll out on a floured surface and cut with cookie cutters
Transfer cut-outs to an ungreased cookie sheet (tip: cookies are less likely to stick to your countertop if you line it with parchment paper!)
Gather scraps into a ball, roll again, and cut out.
Repeat until all the dough is used.
Bake for 12 minutes until the edges are set, and cookies look dry, but before they begin to brown
Remove from oven, transfer to a wire rack, and let cool
While cookies cool, beat glaze ingredients together
Drizzle over cookies, and top with crushed candy canes