Allow your oven to preheat to 350 degrees while you prepare the cookie dough.
Using an electric hand mixer or stand mixer, combine the butter and granulated sugar in a large bowl. Mix the ingredients on a low speed to start and work up to a medium-high speed until the butter is broken into small pieces.
Add the egg and 1 teaspoon of the peppermint extract. Mix again until the egg is fully incorporated into the cookie dough.
Add the flour, cocoa powder, and baking powder. Gently mix the dry ingredients into the wet ingredients until the cookie dough is homogenous.
Form the cookie dough into balls about 1 inch in diameter. Place the balls of dough on a cookie sheet 8 at a time and press them down with a glass so that they form discs. Place the cookie sheet in the freezer for 15 minutes to allow the dough to chill.
Bake the cookies for 10 minutes while you prepare the peppermint chocolate coating. In a small bowl, combine the chocolate chips, vegetable oil, and remaining peppermint extract. Microwave the ingredients on 30 second intervals until fully melted.
Allow the cookies to chill in the freezer for an additional 10 minutes after they come out of the oven before dipping the top of each cookie in the chocolate mixture. Return the coated cookies to the freezer for 10 minutes, or until the chocolate has set.
Serve and enjoy!