Preheat the oven to 350º. This initial step sets the stage for perfectly baked cupcakes.
Prepare your baking tins. Line two muffin tins with 14 liners, or alternatively, line one muffin tin with 12 liners and two ramekins with liners. This ensures easy removal after baking.
In a medium bowl, whisk together the cocoa powder, flour, baking soda, baking powder, and salt until well combined. This mixture forms the dry base of your batter.
In a large bowl, whisk together the eggs, sugar, vegetable oil, and both vanilla and coffee extracts. This creates a sweet, wet mixture that will blend with the dry ingredients.
Gradually whisk about one-third of the dry mixture into the wet mixture, ensuring everything is well incorporated before adding the next ingredients.
Next, add half of the buttermilk to the bowl, mixing it in thoroughly.
Add another third of the dry mixture, followed by the remaining buttermilk, and finally, the last of the dry ingredients. Mix gently after each addition, being careful not to overmix, as this can lead to dense cupcakes.
Fill each cupcake liner about halfway with the batter, ensuring they have room to rise while baking. This should prevent overflow.
Pop the cupcakes into the oven and bake for 18 to 20 minutes. To check for doneness, insert a toothpick in the center; if it comes out clean, they’re ready!
Once baked, remove the cupcakes from the oven and let them cool in the tins for about 10 minutes. After that, transfer them to a wire rack to cool completely.
While the cupcakes are cooling, prepare the buttercream frosting. Beat the butter using the paddle attachment of a stand mixer or a hand mixer until it’s fluffy, which should take about 2 to 3 minutes.
Slowly add in 4 and ½ cups of powdered sugar, cream, and vanilla extract while the mixer runs on low speed. This prevents a cloud of sugar from poofing out.
After combined, increase the speed to high and beat for another couple of minutes until fluffy and smooth. You can adjust the texture by adding more powdered sugar or a touch more cream until it reaches your desired consistency.
Once the cupcakes are completely cooled, frost them using your favorite technique. You can pipe on beautiful swirls or simply spread a generous amount of frosting on top with a knife.