For the cupcakes:
- 12 tablespoons butter (1 1/2 sticks), at room temperature
- 2/3 cup sugar
- 2/3 cup brown sugar
- 2 eggs
- 2 teaspoons vanilla
- 1 cup buttermilk (or 1 cup milk with 1 tablespoon lemon juice, allowed to sit at room temperature for 15 minutes, then shaken vigorously)
- 1/2 cup plain nonfat Greek-style yogurt
- 2 tablespoons brewed coffee (or buttermilk for a substitute if you don't have coffee)
- 1 3/4 cups flour
- 1 cup unsweetened cocoa powder
- 1 1/2 teaspoons baking soda
- 1/2 teaspoon salt
For the frosting:
- 1 cup confectioners' sugar
- 1 cup creamy peanut butter
- 5 tablespoons butter, at room temperature
- 1 teaspoon pure vanilla extract
- 1/4 teaspoon kosher salt
- 1/3 cup half-and-half
To make the cupcakes: Pre-heat the oven to 350°F.
Line the cupcake pans with paper liners. In the bowl of an electric mixer fitted with a paddle attachment, cream the butter and sugars on high speed until light and fluffy, approximately 5 minutes. Lower the speed to medium; add the eggs one at a time, then add the vanilla and mix well. In a separate bowl, whisk together the buttermilk, yogurt and coffee (or additional buttermilk). In another bowl, whisk together the flour, cocoa, baking soda and salt. On low speed, add the buttermilk mixture and the flour mixture alternately in thirds to the mixer bowl, beginning with the buttermilk mixture and ending with the flour mixture. Mix only until blended - do not over mix. Fold the batter with a rubber spatula to be sure it's completely blended. Divide the batter among the cupcake pans (1 rounded standard ice cream scoop per cup is the right amount). Bake in the middle of the oven for 18-25 minutes, until a toothpick comes out clean. Cool for 10 minutes; remove from the pans and allow to cool completely before frosting.
Make the frosting: Place the confectioners' sugar, peanut butter, butter, vanilla and salt in the bowl of an electric mixer fitted with a paddle attachment. Mix on medium-low speed until creamy, scraping down the bowl with a rubber spatula as you work. Add the half-and-half and beat on high speed until the mixture is light and smooth. Frost the cupcakes. Store in an airtight container for up to 3 days at room temperature.