Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.
In a large bowl, sift together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.
In another bowl, beat the softened butter with an electric mixer until creamy. Gradually add the sugar mixture and continue to beat until light and fluffy.
Add the eggs one at a time, mixing well after each addition. Then add the vanilla extract and mix until fully incorporated.
Gradually add the dry mixture to the butter mixture, alternating with buttermilk, starting and ending with the dry mixture. Mix just until combined.
Gently fold in the peanut butter and chocolate chips until evenly dispersed.
Spoon the batter into the lined muffin tin, filling each cup about two-thirds full.
Bake for 18–20 minutes, or until a toothpick inserted in the center comes out clean.
Allow the cupcakes to cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.
Once cooled, swirl additional peanut butter on top of each cupcake and sprinkle with chopped peanuts for extra crunch.
Notes
Swirl additional peanut butter on top for extra flavor.