Chocolate Sour Cream Cupcakes with Mint Swiss Buttercream
Serves: 24
For the cupcakes:
  • ½ cup unsalted butter, soften
  • 1½ cups granulated sugar
  • ½ cup light brown sugar
  • 2 large eggs
  • 1 teaspoon pure vanilla extract
  • ½ cup whole milk
  • 1 cup sour cream
  • 1 teaspoon baking soda
  • ½ teaspoon salt
  • 2 tablespoons cocoa powder
  • 2 cups all-purpose flour
  • 2 ounces bittersweet chocolate, grated or chopped
For the swiss buttercream:
  • 6 egg whites
  • 1¼ cups granulated sugar
  • 10 large mint leaves
  • ¾ cup (3 sticks) diced unsalted butter, slightly softened but not melted
For the cupcakes:
  1. Preheat oven to 350 degrees F. Line 2 cupcake pans with 24 cupcake liners.
  2. With an electric mixer, mix the butter, granulated sugar, and brown sugar on medium speech until smooth, about 3 to 4 minutes. Add the vanilla extract and the eggs, one egg at a time. Reduce the speed to medium-low and add the milk and sour cream. Mix until incorporated, about 2 minutes, stopping once or twice to scrape the sides of the bowl with an offset spatula.
  3. In a small bowl, whisk together the baking soda, salt, cocoa powder, and flour. Slowly add it to the wet mixture, and continue to mix on medium speed until just incorporated. Stir in the chocolate.
  4. Fill each cupcake tin halfway with the batter. Bake for 19-21 minutes, or until a toothpick or knife inserted in the center comes out clean. Allow the cupcakes to cool in the pan for 20 minutes, then transfer to a wire rack to finish cooling.
For the swiss buttercream:
  1. With an electric hand mixer on medium speed, mix the egg whites, sugar, and mint leaves in a glass or steel bowl over simmering water until the egg white mixture reaches 160 degrees F.
  2. Take the bowl off the heat. Remove and discard the mint leaves. With an electric mixer on medium-high speed, whip the egg whites until they become fluffy and double in volume. Turn off the mixer, and allow the egg mixture to cool to room temperature, about 15-20 minutes.
  3. Using an electric mixer again, whip the egg mixture over medium speed and slowly add the cubes of butter, a few at a time. Mix until the buttercream is stiff and very thick, about 8 minutes. If the mixture is too runny and/or won't thicken up, place the bowl in the refrigerator for about 15 minutes, then re-whip until it comes together.
  4. Pipe or spread over the cooled cupcakes. Garnish the cupcakes with extra mint leaves or grated chocolate.
Recipe by Sprig and Flours at