• Microwave butter in heatproof bowl for 30 seconds on high until full melted. Allow to cool for a few minutes.
• Add sugar and mix until combined. Add egg yolk, peppermint extract, and vanilla and mix until combined.
• Add flour, salt, baking powder, and cocoa powder. Mix until combined. Gently shape mixture into a ball.
• Put a sheet of wax paper on counter. Place the dough on the center of the wax paper. Put another piece of wax paper on top of the dough. Gently roll dough out until it's around 1/4 inch thickness. Place on baking sheet and refrigerate for at least 3-4 hours. Chilling is mandatory.
• Cut the cookie dough into circles. Use a 2 inch round cookie cutter. Re-roll the remaining dough until you have roughly 18 cookies. Place cookies on a baking sheet and in the freezer for about 10 minutes before baking them.
• Preheat oven to 350° F. Bake for 10 minutes. Rotate the baking sheet halfway through so they bake evenly. Allow to cool completely before the next step.

Chocolate coating

• Add chocolate chips, peppermint extract, and vegetable oil to a glass bowl. Melt over a double broiler. For the microwave, melt in 15 second increments, stirring each time until completely melted and smooth.
• Dip each cookie completely into the chocolate. Use a fork to lift out. Gently tap the fork on the bowl to allow excess chocolate to drip off. Place on a baking sheet lined with parchment paper.
• Place the baking sheet in the refrigerator to help the chocolate set. After 10 minutes, add any extra chocolate to a piping bag (or plastic bag) and drizzle a bit across the top.
• Cover and store cookies in an airtight container for up to 3 days or in the refrigerator for up to a week. They taste even better cold!