Instructions

• Preheat the oven to 350°F. Line two muffin pans with cupcake liners and lightly spray the liners with nonstick cooking spray.
• In a large mixing bowl, whisk together 3 cups cake flour, 1/2 cup granulated sugar, 1/2 cup packed light brown sugar, 1 1/2 teaspoons baking powder, 1/2 teaspoon baking soda, and 1 teaspoon salt until evenly combined.
• Add 3/4 cup (1 1/2 sticks) unsalted butter, melted, and 1/4 cup vegetable or canola oil to the dry ingredients. Beat or whisk until blended; the mixture will be thick.
• Add 1 cup creamy peanut butter and mix until fully incorporated and uniform in texture.
• Add 3 eggs, one at a time, beating well after each addition and scraping down the sides of the bowl as needed.
• Beat in 2 teaspoons vanilla extract, 1 cup sour cream, and 1/4 cup buttermilk until the batter is smooth and evenly mixed.
• Fold in 1 cup miniature chocolate chips with a spatula until evenly distributed.
• Divide the batter among the prepared cupcake liners, filling each about two-thirds full.
• Bake the cupcakes at 350°F for 22–25 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
• Remove the pans from the oven and let the cupcakes cool in the pans for 5–10 minutes, then transfer the cupcakes to a wire rack to cool completely before frosting.
• For the peanut butter frosting: in a large mixing bowl, beat together 1 cup creamy peanut butter and 1 cup (2 sticks) unsalted butter, room temperature, until creamy and smooth.
• Add 1/8 teaspoon salt and 3 cups powdered sugar to the bowl in about 1/2-cup increments, beating after each addition and scraping the sides of the bowl, until the frosting is smooth and holds its shape.
• Add 2 tablespoons milk and beat for about 1 minute more, until the frosting is light and fluffy. If the frosting is too stiff, beat a little longer or chill briefly; if it is too loose, chill briefly to firm it.
• Transfer the frosting to a piping bag fitted with a 1M Wilton tip (or spread with a spatula) and decorate the cooled cupcakes. Sprinkle additional miniature chocolate chips on top if desired.