Preheat your oven to 350º F and position the oven rack in the middle. This ensures even baking for your cupcakes.
Line a regular muffin tin with 12 cupcake liners. This step is crucial for easy removal after baking. Ensure they’re evenly spaced in the pan.
In a medium mixing bowl, whisk together cocoa powder, flour, baking powder, baking soda, and salt. This allows all the dry ingredients to combine evenly, helping to avoid clumps in your batter.
In a large mixing bowl or using a stand mixer, combine peanut butter, vegetable oil, and brown sugar. Beat this mixture together until it’s well combined and fluffy. This will create a strong base for your cupcakes.
Add the eggs one at a time, mixing well after each addition, and then add the vanilla. This method ensures that the eggs are fully incorporated, giving your cupcakes a rich flavor.
Now it’s time to add the flour mixture and buttermilk alternately. Start with a third of the flour mixture, then half of the buttermilk, and continue alternating until everything is combined. This helps to keep the batter light and airy.
Fill each cupcake liner almost to the top with the batter, maintaining an even distribution across all liners for uniform cupcakes.
Place the muffin tin in the preheated oven and bake for 15 to 17 minutes. Check for doneness by inserting a toothpick; it should come out with a few crumbs.
After baking, allow the cupcakes to cool in the pan for 3 minutes before transferring them to a cooling rack. Flip them upside down on the rack to create a dome top, which is visually appealing.
For the frosting, in a new mixing bowl or clean mixer, combine unsalted butter and vegetable shortening, beating until fluffy. This will be the base for the frosting.
Add in the peanut butter and vanilla, mixing until well combined. This gives the frosting a creamy and rich flavor that perfectly complements the cupcakes.
Slowly add the powdered sugar, one cup at a time, mixing on low speed. Increase to medium speed until the frosting reaches your desired sweetness.
Transfer half of the frosting to another bowl and mix in cocoa powder for a chocolate-flavored frosting. This allows you to have both chocolate and peanut butter flavors.
Using a piping bag fitted with a large star tip, fill one side with the chocolate frosting and the other with the peanut butter frosting. You want to create a beautiful swirl effect on the cupcakes.
Pipe the frosting onto each cupcake, starting in the center and swirling to the outside, then back to the center. This creates a lovely visual effect and ensures each cupcake is generously frosted.
Finally, garnish each cupcake with a Peanut Butter Cup on top for that extra touch of indulgence. Refrigerate the cupcakes for at least 2 hours before serving to let the flavors meld together.
Enjoy your delicious Dark Chocolate Peanut Butter Cupcakes!