Whisk the dry ingredients. In a large mixing bowl, sift the flour, cocoa powder, baking powder and salt in a medium bowl and whisk until combined.
Cream the butter and wet ingredients In a large bowl or the bowl of your stand mixer with a paddle attachment, add the room temperature butter and sugar and beat with the stand mixer or a hand mixer on medium high speed until creamy about 2 minutes. Next, add the egg, vanilla, and peppermint extract. Continue to beat until combined about 1 minute. Scrape down the sides and mix to thoroughly incorporate all the ingredients.
Combine the ingredients. Pour in the dry ingredients Reduce the speed to low and continue mixing until just incorporated. Scrape down the sides and mix as needed.
Divide the dough in half and roll out. Divide the dough in half. On a piece of parchment paper, roll each half into 1/4 inch thickness. Leaving the dough on the parchment papers, place the dough on top of each other and chill in the refrigerator for at least 1 1/2 hours or in the freezer for 1 hour.
Prepare the oven. Preheat the oven to 350°F (177°C). Line 2-3 large baking sheets with parchment paper or silicone baking mats.
Cut the cookies. Remove one of the slabs of dough from the refrigerator and cut the dough into 2-inch circles. Transfer to the prepared baking sheet. Re-roll and continue cutting until all is used. Chill the cookies in the refrigerator for 10 minutes.
Bake. Bake the cookies one tray at a time for 10-12 minutes or until the edges appear set. The cookies may seem soft and underdone in the center but that's okay! Cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely before dipping the chocolate.
Melt the chocolate and dip the cookies. Melt the chocolate and oil together in a double boiler or use the microwave. For the microwave, microwave the chocolate and oil in 15 second increments, stirring after each increment until completely melted and smooth. Once the chocolate has melted stir in the peppermint extract. Dip the cookies completely in the chocolate and use a fork to lift them out. Place the cooke onto a parchment or silicone mat lined baking sheet. (Optional) Sprinkle crushed candy canes on top for holiday cheer! Chill in the refrigerator to set.