Peanut Butter Cupcakes

and 1/4 cups (155g) all-purpose flour

baking soda

salt

(120ml) canola or vegetable oil*

(125g) creamy peanut butter*

packed light or dark brown sugar

large egg, at room temperature

(45g) sour cream, at room temperature

and 1/2 teaspoons pure vanilla extract

(180ml) whole milk, at room temperature*

very finely crushed or chopped peanuts*

unsalted butter, softened to room temperature

and 1/2 cups (420g) confectioners' sugar

unsweetened natural or dutch-process cocoa powder

heavy cream or milk

cup creamy peanut butter*

pure vanilla extract

salt

optional for garnish: mini Reese's Peanut Butter Cups or chopped peanuts