Chocolate Whiskey Cupcakes
Yield: 24 cupcakes
For the cupcakes:
1 cup unsweetened cocoa powder
2 tsp. espresso powder
1 cup boiling water
½ cup sour cream
2 tsp. vanilla extract
1¼ cups all-purpose flour
¾ tsp. baking soda
½ tsp. salt
16 tbsp. unsalted butter, at room temperature
1¾ cups sugar
2 large eggs
For the whiskey simple syrup:
½ cup water
½ cup sugar
2 tbsp. whiskey
For the frosting:
2 large eggs, at room temperature
2 large egg yolks, at room temperature
¼ cup water
1 cup sugar
3 sticks (18 tbsp.) unsalted butter, at room temperature
Pinch of salt
3-4 tbsp. whiskey
To make the cupcakes, preheat the oven to 350˚ F. Line two cupcake pans with paper liners (24 total). Combine the cocoa powder and espresso powder in a small bowl. Add the boiling water and whisk until the mixture is smooth. Set aside and let cool to room temperature. Once cool, whisk in the sour cream and vanilla extract.
Combine the flour, baking soda and salt in a small bowl. Stir together with a fork to combine; set aside.
In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and sugar. Beat on medium-high speed until light and fluffy, 3-5 minutes. Beat in the eggs 1 at a time, beating well after each addition and scraping down the bowl as needed.
With the mixer on low speed, mix in the dry ingredients in three additions, alternately with the cocoa-sour cream mixture, beginning and ending with the dry ingredients. Beat each addition just until incorporated. Divide the batter evenly between the prepared cupcake liners. Bake 18-20 minutes, until a toothpick inserted in the center comes out clean. Let cool in the pan 5-10 minutes, then transfer to a wire rack to cool completely.
To make the simple syrup, combine the water and sugar in a small saucepan. Heat over medium-high heat, stirring occasionally, until the mixture is warm and the sugar has dissolved. Remove from the heat and stir in the whiskey. Set aside and let cool until ready to use.
To make the frosting, combine the eggs and egg yolks in the bowl of a stand mixer fitted with the whisk attachment. Whisk on high speed about 5 minutes. In a small saucepan, combine the water and sugar. Heat, stirring frequently, until it reaches the soft-ball stage, 234˚-239˚ F. Immediately transfer the sugar syrup to a liquid measuring cup. With the mixture on low speed, add the sugar mixture to the egg mixture in a slow, thin stream. Increase the speed to medium and beat about 7 minutes, until the syrup has cooled and the bowl is just barely warm to the touch. Add the butter 3-4 tablespoons at a time, beating well after each addition, at least 30 seconds. Once all of the butter has been added, continue to beat on medium speed until the frosting thickens slightly, 3-5 minutes. Blend in the salt and whiskey.
To assemble the cupcakes, brush the cooled cupcakes with the whiskey syrup. Pipe the frosting onto the cupcakes using a pastry bag. Refrigerate until ready to serve.