- 2/3 cup confectioners’ sugar
- 1 cup heavy cream
- 1 cup buttermilk
- 1 and 3/4 cups all-purpose flour
- 8 ounces semisweet chocolate, chopped
- 1 and 1/4 teaspoons baking soda
- 1 cup creamy peanut butter
- 1/4 teaspoon salt
- 1 and 1/2 sticks plus 3 tablespoons unsalted butter, softened
- 1 and 1/2 cups granulated sugar
- 2 large eggs, at room temperature
- 3/4 cup plus 2 tablespoons cocoa powder (not Dutch process)
- 1/2 cup boiling water
- 1/4 teaspoon baking powder
- 1 teaspoon pure vanilla extract
In the first, preheat the oven to 350° and position 2 racks in the lower and middle third of the oven and line 24 muffin cups with paper or foil liners.
Then put the cocoa powder in a medium heatproof bowl and add the boiling water and whisk until a smooth paste forms. Whisk in the buttermilk until combined and then in a medium bowl, sift the flour with the baking powder, baking soda and salt.
Now, in a large bowl, using an electric mixer and beat 1 and 1/2 sticks of the butter with the granulated sugar until light and fluffy, about 3 to 5 minutes. Beat in the eggs and some vanilla, and then beat in the dry ingredients in 2 batches, alternating with the cocoa mixture. Then carefully spoon the cupcake batter into the lined muffin cups and filling them about two-thirds full. Then bake for 20 to 22 minutes, or until the cupcakes are springy and let the cupcakes cool in the pans for 5 to 7 minutes, then transfer them to wire racks to cool completely.
In a medium bowl, beat the peanut butter with the remaining 3 tablespoons of butter until creamy. Then sift the confectioners’ sugar into the bowl and beat until light and fluffy, about 2 to 3 minutes and spoon all but 3 tablespoons of the peanut butter filling into a pastry bag fitted with a 1/4-inch star tip and holding a cupcake in your hand, plunge the tip into the top of the cake, pushing it about 3/4 inch deep. Gently squeeze the pastry bag to fill the cupcake, withdrawing it slowly as you squeeze and you will feel the cupcake expand slightly as you fill it. Scrape any filling from the top of the cupcake and repeat until all of the cupcakes are filled.
At last in a small saucepan, bring the heavy cream to a simmer and off the heat and add the semisweet chocolate to the cream and let stand for 5 to 7 minutes, and then whisk the melted chocolate into the cream until smooth and let the chocolate icing stand until slightly cooled and thickened, about 15 to 18 minutes. Dip the tops of the cupcakes into the icing, letting the excess drip back into the pan. Then transfer the cupcakes to racks and let stand for 5 to 7minutes. Then dip the tops of the cupcakes again and transfer them to racks. Spoon the remaining 3 tablespoons of peanut butter filling into the pastry bag and pipe tiny rosettes on the tops of the cupcakes.