Wintermint Cake
Author: 
Yield: 1 8-inch three-layer cake • 10 to 12 servings
 
Ingredients
For the Classic Chocolate Cake
  • ½ cup (40 g) unsweetened dark cocoa powder (such as Valrhona) plus ¼ cup (20 g) unsweetened black cocoa powder; or just ¾ cup (60 g) unsweetened dark cocoa powder
  • 1¼ cups (300 ml) hot water
  • ⅔ cup (150 g) sour cream
  • 2 2⁄3 cups (340 g) all-purpose flour
  • 2 teaspoons baking powder
  • 1 teaspoon baking soda
  • ½ teaspoon kosher salt
  • 6 ounces (1½ sticks/170 g) unsalted butter, softened, plus more for the pans
  • ½ cup (100 g) unflavored vegetable shortening
  • 1 ½ cups (300 g) granulated sugar
  • 1 cup (220 g) firmly packed dark brown sugar
  • 3 large eggs, at room temperature
  • 1 tablespoon pure vanilla extract
For the Peppermint Buttercream
  • 1½ cups (300 g) granulated sugar
  • 1⁄3 cup (40 g) all-purpose flour
  • 1½ cups (360 ml) whole milk
  • 1⁄3 cup (75 ml) heavy cream
  • 12 ounces (3 sticks/340 g) unsalted butter, soft but cool, cut into ½-inch (12-mm) cubes
  • 1 teaspoon pure vanilla extract
  • 1 teaspoon pure peppermint extract (not mint or spearmint extract)
  • Food dye or gel
For the Peppermint Chocolate Ganache
  • 6 ounces (170 g) dark chocolate (60 to 72% cacao), coarsely chopped
  • ½ cup (120 ml) heavy cream
  • 1 tablespoon crème de menthe (optional)
  • ½ teaspoon pure peppermint extract
Instructions
Make the Classic Chocolate Cake
  1. Preheat the oven to 325°F (165°C).
  2. Butter three 8-inch (20-cm) round cake pans, line them with parchment, and butter the parchment. Dust with flour and knock out and discard excess flour.
  3. In a small bowl, mix the cocoa powder, hot water, and sour cream together and set aside to cool.
  4. In a large bowl, sift the flour, baking powder, baking soda, and salt and set aside.
  5. In the bowl of a standing mixer fitted with the paddle attachment, beat the butter and shortening together on medium speed until light and smooth, about 5 minutes; the mixture will appear to string or ribbon throughout the bowl. Add both sugars and beat until light and fluffy, about 5 more minutes. Add the eggs one at a time, beating after each until incorporated, then add the vanilla and beat together. Scrape down the sides of the bowl and mix again for 30 seconds. Add the flour mixture in three parts, alternating with the cocoa mixture, beginning and ending with the flour mixture, beating to incorporate after each addition. Scrape down the bowl and beat for a few more seconds.
  6. Divide the batter among the three prepared pans (about 1¼ pounds/565 g of batter per pan). Use your spatula to spread the batter evenly. Bake, rotating the pans halfway through, until a toothpick inserted in the center of the cakes comes out clean, 35 to 40 minutes. Transfer the cakes to a wire rack and let cool for 20 minutes. Invert the cakes onto the rack and let them cool completely. Remove the parchment.
  7. Make the Peppermint Buttercream
  8. In a medium heavy-bottomed saucepan, whisk the sugar and flour together. Add the milk and cream and cook over medium heat, whisking constantly but gently, until the mixture comes to a boil and has thickened, 8 to 12 minutes.
  9. Transfer the mixture to the bowl of a standing mixer fitted with the paddle attachment. Beat on high speed until cool, at least 7 to 9 minutes of mixing; you can speed up the process by pressing bags of frozen berries or corn against the sides and bottom of the mixing bowl. Reduce the speed to low and add the butter a few cubes at a time, beating well after each addition. Once all of the butter is thoroughly incorporated, increase the speed to medium-high and beat until the frosting is light and fluffy, 1 to 2 minutes. Add the vanilla and peppermint extracts and continue mixing until combined. If the frosting is too soft, put the bowl in the refrigerator to chill slightly, then beat again until it is the proper consistency; if the frosting is too firm, set the bowl over a pot of simmering water and beat with a wooden spoon until it is the proper consistency.
Make the Peppermint Chocolate Ganache
  1. Place the chocolate in a medium heatproof bowl and set aside.
  2. In a small saucepan over medium heat, bring the cream just to a boil. Remove from the heat and pour it over the chocolate. Let the cream sit for 2 to 4 minutes, then, starting in the center of the bowl and working your way out to the edges, slowly stir the chocolate-and-cream mixture in a circle until the chocolate is completely melted and the mixture is smooth. Whisk for another few minutes to release the excess heat from the mixture. Stir in the crème de menthe, if using, and the peppermint extract. Let the ganache come to room temperature, whisking occasionally, about 15 minutes.
Assemble the Cake
  1. Place one cake layer on a serving platter (or, better yet, a cake turntable). Trim the cake layer to create a flat top surface. Use an offset spatula to spread about ¼ cup (60 ml) of the mint chocolate ganache on the top (not sides) of the layer. Put the cake in the refrigerator to set the ganache for a few minutes. Remove from the refrigerator and spread approximately 1¼ cups (160 g) of the peppermint buttercream on top of the ganache. Top with the next cake layer, trim, add ganache, chill, and then add buttercream as with the first layer. Then add the third layer and trim the top. Spread a very thin layer of peppermint buttercream (known as crumb coating) over the sides and top of the cake and put it in the refrigerator to firm up for about 15 minutes.
  2. To frost the cake ombré-style, distribute the remaining frosting into three separate bowls, putting about ¼ cup (30 g) more frosting in one bowl than in the other two. Add a few drops of food dye to each bowl and mix to create three different shades of pink: dark, medium, and light; the one with slightly more frosting should be the light pink. Obviously, if pink is not your color, you can use any color on the spectrum.
  3. Starting with the bottom of the cake, apply a band of the dark pink frosting up one-third of the cake and all the way around. Wipe the spatula. Apply an equal band of medium pink frosting above the dark pink frosting and wipe the spatula. Then apply an equal band of light pink frosting above the medium pink band, bringing it all the way up to the top edge of the cake. Wipe the spatula. Immediately, use an offset spatula to smooth the bands (you can spin the cake turntable against the edge of the offset spatula to make this step easier; while continuing to smooth the color bands, bring some of the light pink frosting up and just slightly over the top of the cake.
  4. Using the same offset spatula, wiping it as necessary, start from the bottom and dimple the cake in even rows up the sides of the cake (if you are using a cake turntable, rotate the cake and just lift and press with the curved end of the spatula).
  5. Finally, once all of the dimples have been applied to the sides of the cake, spread the remaining light pink frosting over the top of the cake (you might need to add a smidge more light pink icing to your spatula as you work) and continue the dimpling process in toward the center.
  6. To frost the cake more conventionally (not ombré-style), follow the instructions in step 1 to apply the crumb coat. Frost the sides and top of the cake with the remaining buttercream, and refrigerate for about 15 minutes to firm up the entire cake.
Notes
How to store: this cake will keep beautifully in a cake saver at room temperature for up to 3 days, as long as the weather is cool and humidity-free. Otherwise, place it in a cake saver and refrigerate it for up to 3 days; let the chilled cake sit at room temperature for at least 2 hours before serving.
Recipe by Baked Sunday Mornings at http://bakedsundaymornings.com/2014/12/09/oven-wintermint-cake/