Crisp Chocolate-Mint Cookies

In the bowl of a stand mixer fitted with the paddle attachment, cream together butter and sugar on medium-high speed until light and fluffy, 3 to 4 minutes. Add vanilla and mint extracts and mix to incorporate. In a medium mixing bowl, whisk together flour, cocoa powder, baking powder, and salt. With the mixer speed on low, add the dry ingredients and mix until just combined. Turn the dough out onto a work surface and form into a disc. Wrap in plastic wrap and refrigerate for at least one hour. Preheat oven to 325degrees F. Line baking sheets with parchment paper. Let dough rest at room temperature for a few minutes so it is soft enough to roll. Roll cookie dough to 1/4-inch thickness on a lightly floured surface and cut dough into 2-inch circles. Transfer cookie dough to prepared baking sheets. Chill cookies on the pans for 20 minutes. Bake cookies for 20 minutes. Cool on the pan for 10 minutes, then transfer to a wire rack to cool completely. Line a baking sheet with parchment or wax paper. Place chocolate chips in a microwave-safe bowl and heat in the microwave, stirring every 15 seconds, until melted and smooth. Stir oil into the chocolate to thin it out to a dipping consistency. Dip each cookie in chocolate with a fork, shake off any excess chocolate back into the bowl, and transfer cookies onto the prepared baking sheet. Let set up at room temperature or chill in the refrigerator.