Easy to make peanut butter cupcakes topped with smooth and creamy peanut butter buttercream. For the ultimate peanut fan, sprinkle these cupcakes with chopped peanuts!
Preheat oven to 350°F. Line muffin tin with cupcake paper liners. Set aside.
In a large bowl, whisk together flour, baking powder, and salt. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment (or using an electric hand mixer), beat together butter, oil, and peanut butter until combined. Add brown sugar and sugar. Beat until smooth. Scrape down sides of bowl as needed. Add egg. Beat until incorporated.
In a small bowl, whisk together milk, sour cream, and vanilla.
Alternate adding dry and wet ingredients. Add 1/3 of flour mixture. Mix on low speed. Add 1/2 of wet ingredients. Mix until combined. Repeat adding dry and wet, finishing with the last 1/3 of flour mixture. Scrape down sides of bowl as needed. Mix until just combined and there are no longer and dry streaks of flour.
Divide batter among 12 cupcakes, filling liners about 2/3 full. Bake for 20-22 minutes, until toothpick inserted in center of cupcake comes out clean. Cool cupcakes in tin for 5 minutes. Remove cupcakes from tin and cool to room temperature on wire racks.
In the bowl of a stand mixer fitted with paddle attachment (or using an electric hand mixer), heat butter until smooth. Add peanut butter and beat until well combined.
Add confectioners sugar, milk, vanilla, and salt. Beat until buttercream is smooth. Scrape down sides of bowl to ensure thorough mixing.
*If buttercream is too thick, add additional tablespoon of milk until desired consistency is achieved.
Use a #40 scoop (1½ Tbsp) to portion out buttercream. Add a scoop atop each cooled cupcake. Use a mini offset spatula or the back of a spoon to spread buttercream over cupcake.
Decorate cupcakes as desired.