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1
Preheat oven to 375.
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2
Line 3 standard 12-cup muffin tins with paper liners.
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3
Make the cupcakes: Whisk flour, baking powder, salt, and baking soda in a medium bowl.
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4
Put butter and sugar into the bowl of an electric mixer fitted with the paddle attachment; mix on medium speed until pale and fluffy.
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5
Reduce speed to low.
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6
Mix in peanut butter.
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7
Mix in eggs, 1 at a time, and vanilla.
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8
Add flour mixture; mix until combined.
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9
Mix in sour cream.
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10
Spoon scant 3 tablespoons batter into each muffin cup.
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11
Bake until pale golden and a cake tester inserted into centers comes out clean, about 13 minutes.
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12
Transfer to wire racks; let cool completely.
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13
Make the frosting: Put cream cheese, confectioners sugar, and butter into the clean bowl of a mixer fitted with the clean paddle attachment; mix on medium- high speed until pale and fluffy.
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14
Stir in peanut butter with a rubber spatula.
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15
Spread 1 1/2 tablespoons frosting onto each cupcake.
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16
Refrigerate until frosting is firm, about 10 minutes.
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17
Using tines of a fork dipped in confectioners sugar, score each top in a crosshatch pattern.
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18
Cupcakes can be refrigerated in single layers in airtight containers up to 2 days.
