Preheat oven to 350 ℉. Line muffin tin with paper liners. Set aside.
Whisk together flour, baking powder, and salt in a medium-sized bowl. Set aside.
Cream the butter using an electric mixer at medium speed until light and fluffy. Add the peanut butter and continue to blend until smooth. Add brown sugar and granulated sugar. Beat until creamy.
Add in eggs one at a time, scraping down bowl as needed to ensure thorough mixing. Add in vanilla.
Add half of the flour mixture to mixing bowl. Mix until almost combined. Add in sour cream and milk. Mix until incorporated. Add remaining flour mixture. Beat until just combined and there are no longer any dry streaks of flour.
Use a #20 size scoop to evenly divide the batter among the lined cupcake pan.
Bake for 18-20 minutes until cupcakes are light gold in color. Test the center with a toothpick and make sure it comes out clean. Remove cupcakes from pan and let cool on rack before frosting.
Dark Chocolate Ganache:
Place chopped chocolate in a small bowl.
Bring the cream to a boil and pour over chocolate. Cover bowl with plastic wrap and let side for about a minute.
Using a heat-resistance spatula stir the mixture until smooth. Begin in one spot, stirring in a small circle, then gradually increasing size of circle. Cover the bowl with plastic wrap. Place ganache in the fridge for about 45 minutes.
Chocolate mixture should have firmed up and thickened substantially. If mixture is still soft, return to fridge for another 15-30 minutes. Use a hand mixer or the paddle attachment of a stand mixer to beat ganache until smooth, creamy, and fluffy (about 8 minutes on hand mixer or 5 minutes on stand mixer).
Fill a piping bag with a medium star tip and pipe on cooled cupcake. Top with chopped peanuts.
Notes
Ingredients:
Salt: This recipe was created using Diamond Crystal kosher salt. Use half the amount if using table salt or Morton's kosher salt.
Peanut Butter: Best to use a no-stir shelf stable creamy peanut butter like Jif or Skippy.
Chocolate: Use your choice of semi-sweet, bittersweet, or dark chocolate.
Storage and Leftovers:
Unfrosted peanut butter cupcakes may be stored in an airtight container at room temperature for up to three days.
Store frosted cupcakes in an airtight container in the fridge for up to three days. Warm to room temperature before enjoying.