Preheat oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners.

In a large bowl, whisk together the flour, cocoa powder, sugar, baking soda, baking powder, and salt.

In a separate medium bowl, whisk together the egg, buttermilk, vegetable oil, and vanilla extract.

Pour the wet ingredients into the dry ingredients and mix on low speed until just combined. The batter will be thick.

Slowly pour the hot coffee into the batter while mixing on low speed. The batter will be thin, but this is normal.

Fill each cupcake liner about two-thirds full. Bake for 18-22 minutes, or until a wooden skewer inserted into the center comes out clean.

Let cupcakes cool in the pan for a few minutes before transferring them to a wire rack to cool completely.

In a large bowl, beat the softened butter until creamy. Gradually add the powdered sugar, alternating with the heavy cream. Add the peppermint extract and salt. Whip on medium-high speed for 3-5 minutes until light and fluffy.

Once the cupcakes are completely cool, pipe or spread the frosting on top. Garnish with crushed candy canes before serving.