Preheat oven to 350°F and line cupcake cups.
In a large bowl, sift together flour, sugar, cocoa powder, baking soda, baking powder, and salt.
In a medium bowl, whisk together buttermilk, oil, egg, and vanilla.
Add wet ingredients to dry and slowly whisk until combined.
Pour in the coffee and peppermint and whisk until batter is smooth. The batter is going to look alarmingly runny at this point, but don't worry! It's supposed to look like that.
Fill cupcake cups just 2/3 of the way full, no higher. This should make 15-16 cupcakes. If you have one, transferring the batter to a liquid measuring cup and pouring it into the cupcake cups makes this process much tidier!
Bake for 17-20 minutes. Try not to open the oven door too often or jostle the pan while cupcakes are cooking. It can cause them to sink. Cupcakes are done when a toothpick inserted into the center comes out clean. Allow to cool in the cupcake pan on a wire rack before adding chocolate coating.