Using an electric mixer, cream together the butter and sugar on medium speed until light and fluffy. Add egg and vanilla extract, scrape down the sides and bottom of the bowl, and beat again to combine.

Sprinkle the flour, cocoa, baking powder, and salt over the butter-sugar mixture. Mix on low speed just until an even dough forms. Shape dough into a ball, wrap with plastic wrap, and refrigerate for at least 1 hour.

When ready to bake, remove dough from the fridge, preheat oven to 350 degrees F, and line baking sheets with parchment paper or silicone baking mats. Lightly dust a work surface with extra cocoa powder, to prevent the cookies from sticking as you roll out the dough.

Roll the dough into a sheet about 1/4” thick, and cut into 2-3” wide circles using a cookie cutter or small glass. Transfer cut cookies to the prepared baking sheets, re-roll extra dough, and keep cutting until you’ve used it all. (You can also cut into squares to save time!)

Bake cookies for 10 minutes. They’ll be slightly crisp on the edges and appear soft in the centers. Cool for 5-10 minutes on the baking sheets, then transfer to a wire rack to cool completely.

Melt white chocolate according to package directions, and use a spoon to drizzle a small amount over each cookie. Sprinkle immediately with crushed peppermint, and set aside to dry. After about 1 hour, the topping will be set, and the cookies can be easily stacked. They’ll keep well if tightly wrapped at room temperature for 4-5 days.