A moist chocolate cake topped with a mocha-flavored ganache that has been whipped to soft peaks.
For the Cake:
- 1¾ cups all-purpose flour
- 1 teaspoon baking soda
- 1 teaspoon kosher salt
- ¾ cup unsalted butter, at room temperature
- 2 cups granulated sugar
- 1 tablespoon vanilla extract
- 3 eggs, at room temperature
- ⅔ cup hottest tap water
- ⅔ cup unsweetened cocoa powder
- 1 teaspoon instant espresso powder
- ⅔ cup half-and-half
For the Frosting:
- 12 ounces dark chocolate, finely chopped
- 3 tablespoons unsalted butter, cut into small pieces, at room temperature
- 2 teaspoons instant espresso powder
- 1¼ cups heavy cream
- 1 tablespoon Kahlua (optional)
- 1 teaspoon vanilla extract
Make the Cake:
- Preheat oven to 350 degrees F. Grease a 9×13-inch pan; set aside.
- In a medium bowl, sift together the flour and baking soda, then stir in the salt.
- Using an electric mixer, beat the butter and sugar on medium speed for 5 minutes, until light and fluffy. Scrape down the bowl, then add the vanilla and beat in the eggs, one at a time, until incorporated and the batter is smooth.
- In a medium bowl or large liquid measuring cup, whisk together the hot water, cocoa powder and espresso powder until smooth. Add the half-and-half and whisk until smooth.
- With the mixer on low, add the flour and chocolate mixtures alternately in thirds, beginning and ending with the flour. With a rubber spatula, scrape down the bowl and ensure that the batter is well-mixed.
- Pour the batter into the prepared pan, smooth the top, and bake for 20 to 30 minutes, until a cake tester inserted in the center comes out clean. Cool completely in the pan on a wire rack before frosting.
Make the Frosting:
- Place the chocolate, butter and espresso powder in a large bowl. Pour the cream into a small saucepan and place over medium heat until it simmers. Remove from the heat and pour it evenly over the chocolate mixture.
- Let stand for 1 minute, then gently stir with a rubber spatula until everything is melted and smooth. Stir in the Kahlua and vanilla extract until thoroughly combined. Refrigerate for 30 minutes.
- Scrape down the bowl and beat the frosting with a handheld mixer on high speed for ONLY 15 to 20 seconds, until the mixture forms soft peaks (if you overbeat it, it will curdle).
- Immediately spread on the cake and serve. The cake can be stored, covered, at room temperature for up to 4 days.