Old Fashioned Chocolate Layer Cake is a tall and stately two layer chocolate cake adapted from Cook's Illustrated. For best results, use Dutch-process cocoa and real buttermilk.
4large eggs plus 2 large egg yolksat room temperature
12tablespoons168 grams unsalted butter, cut into 12 pieces, at room temperature
Favorite Chocolate Frosting
8tablespoonsunsalted buttersoftened
3cupssifted confectioners’ sugarsift or aerate before using (about 9 oz)
¾cupnatural style cocoa powder
1 ½tablespoonssour creamroom temperature
1pinchof salt
1teaspoonvanilla extract
4 to 6tablespoonsof heavy cream plus more as neededor use a combination of cream and whole milk
Instructions
Preheat oven to 350 F. Grease and flour 2 9x2 inch round cake pans.
In a heatproof bowl set over simmering water or in the top of a double boiler, combine the chocolate, cocoa powder and water. Heat, stirring often, until chocolate melts and mixture is smooth.
Add ½ cup of the sugar to the chocolate mixture and stir until glossy. Remove from heat and let cool slightly.
In a medium bowl, whisk together the flour, baking soda and salt.
In a measuring cup, whisk together the buttermilk and vanilla.
In a stand mixer bowl with whisk attachment or in a large mixing bowl using a handheld mixer, beat the eggs and yolks for 1 minute. Add the remaining 1 ¼ cups of sugar and beat on high for 2 minutes or until mixture is pale and fluffy.
Pour the cooled chocolate mixture into the mixer bowl and beat on medium speed (if using stand mixer, switch to paddle attachment) until well combined. Scrape down the sides of the bowl. Add the butter, one piece at a time, mixing for about 10 seconds after each addition. With the mixer on lowest speed (or by hand), alternately add the flour mixture and the buttermilk mixture starting and ending with the flour mixture. The batter may look slightly curdled. Beat until thoroughly combined.
Divide the batter between the cake pans, smoothing the top until even. Bake for 25-30 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs attached. Remove the pans to a wire rack and let cool for 10 minutes. Turn the cakes out of the pans and let completely, at least 2 hours.
Frosting: To make the frosting, beat the butter until creamy. Gradually add 2 cups of the sugar and beat until well mixed, then add the cocoa powder and beat until mixed – it should look crumbly and pasty. Add the sour cream and salt and beat well, then gradually add the remaining sugar and cream, scraping sides of the bowl, until frosting starts looking smooth and creamy. Taste and adjust sugar and cream as needed.
Notes
I usually make cakes with a handheld mixer. Since my handheld mixer doesn't have a true "low" speed, I mix the flour and buttermilk mixture in by hand (meaning with a heavy duty scraper or mixing soon) to avoid over-beating. If using a stand mixer with a paddle on low speed, you don't run much of a risk of over-beating, so in that case it's fine to just use the paddle.