Prep the Oven and Pan: Start by preheating your oven to 350 degrees F so it is nice and hot by the time your batter is mixed. I always take a moment to line my 12-cup muffin tin with paper liners. This is such an important step because it keeps the chocolate cakes from sticking to the metal and makes it so much easier to clean up the pan once the baking is all done and the cupcakes are cooling.
Whisk the Dry Ingredients: In a medium-sized mixing bowl, whisk together the flour, unsweetened cocoa powder, granulated sugar, baking soda, baking powder, and salt. I like to make sure I get all the little lumps out of the cocoa powder so the cake has a very smooth texture. It’s a simple task, but taking the time to combine everything well now means you won't have any salty or bitter spots in your finished cupcakes later on.
Mix in the Wet Ingredients: In another bowl, whisk together the buttermilk, oil, egg, and vanilla. Slowly pour these wet ingredients into your dry mixture while stirring gently. Just before the flour completely disappears into the batter, pour in the half-cup of coffee. Don't be worried if the batter looks very thin and watery; that is exactly how it is supposed to be. Carefully divide the batter into your 12 muffin cups, making sure they are no more than 3/4 full so they don't spill over.
Bake and Cool: Slide the tin into the center of the oven and bake for about 22 minutes. You can check if they are done by inserting a toothpick into the center of a cupcake; if it comes out clean, they are perfect. Once you pull them out, let them sit in the tin for a few minutes before moving them to a wire rack to cool completely. It is very important that the cupcakes are totally cold before you even think about adding the frosting, otherwise, all that beautiful peanut butter cream will just melt away.
Whip the Buttercream: To make that amazing frosting, put your room temperature butter, confectioner’s sugar, creamy peanut butter, and vanilla into a bowl. Use a hand mixer on high speed to beat everything together for at least three minutes until it looks light, fluffy, and perfectly blended. I love watching the frosting change color as it gets air whipped into it; it becomes so smooth and smells like the best peanut butter treat you’ve ever had in your life.
Decorate and Garnish: Once the cupcakes are cold, you can pipe or spoon the peanut butter buttercream onto each one. I like to be generous with the frosting because it’s so delicious, and then I often add a little drizzle of chocolate syrup on top to make them look fancy. If you want a little extra crunch, you can sprinkle on some chopped peanuts as well. It’s the final touch that makes these cupcakes feel special and ready to be served to your family and friends for a wonderful homemade dessert.
