In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt. Set aside.

1. In a large bowl, beat the softened butter and powdered sugar together until light and fluffy.
2. Add the milk and peppermint extract, and beat until smooth and well combined.
3. Gradually add the dry ingredients to the wet mixture, mixing until the dough comes together. The dough should be firm but soft enough to roll out.
4. Roll the dough between two sheets of parchment paper to about ¼-inch thickness. Use a round cookie cutter to cut out circles, and place them onto a baking sheet lined with parchment paper.
5. Refrigerate the dough for 15-20 minutes to firm up before baking.
6. Preheat your oven to 350°F (175°C).
7. Bake the cookies for 8-10 minutes, or until firm. Let them cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
8. While the cookies are cooling, melt the chocolate chips with the vegetable oil in a heatproof bowl over a pot of simmering water or in the microwave, stirring until smooth.
9. Dip each cooled cookie into the melted chocolate, ensuring it’s fully coated. Allow the excess chocolate to drip off, then place the cookie back on the parchment paper.
10. Once all the cookies are coated, refrigerate them for at least 30 minutes to allow the chocolate to set.