Preheat your oven to 175°C (350°F) and line a muffin tin with paper liners.
Whisk together the cocoa powder and hot brewed coffee until smooth and glossy; set aside to cool slightly.
In a large bowl, beat the softened butter and sugar with an electric mixer on medium speed until light and fluffy, about 3-4 minutes. Add eggs one at a time, beating well after each addition.
Alternate adding the dry flour mixture and buttermilk to the wet mixture, starting and ending with the dry ingredients. Mix just until combined after each addition; the batter should be smooth and velvety.
Divide the batter evenly among the paper liners, filling each about two-thirds full.
Bake the cupcakes for 18-20 minutes, or until a toothpick inserted into the center comes out clean. The tops should be shiny and lightly domed.
Remove the cupcakes from the oven and let them cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
Once cooled, frost the cupcakes with your favorite chocolate or cream cheese frosting for the perfect finishing touch.