Preheat the oven to 350°F. In a bowl, combine the flour, baking powder, salt and cocoa powder. Whisk until smooth.

In a mixing bowl, cream the butter and sugars until light and fluffy. Mix in the egg and peppermint extract. Gradually mix in the dry ingredients until the dough comes together. Use your hands to form the dough into a ball.

Place the ball of dough onto a sheet of parchment paper. Flatten it into a disk and put another piece of parchment paper on top. Use a rolling pin to roll out the dough to ¼-inch thick. Transfer the rolled dough, with the parchment paper, onto a baking sheet. Place the baking sheet in the freezer to chill for 10 minutes.

Transfer the flattened dough to a countertop. Remove the top sheet of parchment paper and use it to line the baking sheet. Use a small, circular cookie cutter to cut out disks of dough. Transfer the cut disks onto the prepared baking sheet, leaving space in between. Place the baking sheet in the oven and bake for 11 minutes. Once baked, remove the cookies from the oven, then transfer the parchment paper and cookies to a cooling rack to fully cool.

While the cookies cool, prepare your chocolate coating. Set up a double boiler and chop the chocolate. Add the chopped chocolate into the bowl of the boiler and stir in the vegetable oil. Stir the chocolate until fully melted and stir in the peppermint extract.

Use a slotted wooden spoon to make the dipping process easier. Place a cookie on the wooden spoon. Dip it into the chocolate or use a large spoon to help cover the cookie. Tap the spoon gently against the bowl to remove excess chocolate. Once covered in chocolate, transfer each cookie back to the baking sheet lined with parchment paper. Place the baking sheet in the fridge for 20 minutes to allow the chocolate to fully set and harden.