In a mixing bowl, beat softened salted butter at medium speed until fluffy, about 2-3 minutes. Gradually mix in sugar until well combined. Add egg and coffee extract, blending until smooth.

In a separate bowl, whisk together all-purpose flour, dark cocoa powder, and baking powder. Gradually add to wet ingredients, mixing on low speed until just incorporated.

Divide dough in half, wrap tightly in plastic wrap, and refrigerate for at least 1 hour.

Preheat oven to 350°F (175°C). Roll out one portion of dough between two sheets of parchment paper to about ¼ inch thickness.

Cut out shapes with cookie cutters and transfer to a baking sheet, leaving space between cookies.

Bake in the preheated oven for 12 minutes. Let cookies cool on the baking sheet for 10 minutes before transferring to a wire rack.

Melt milk chocolate chips in a microwave-safe bowl in 30-second intervals until smooth. Dip tops of cooled cookies in chocolate and coat with nonpareils.