This Devil’s Food-style cake is packed with chocolate flavor. For an accurate measurement of boiling water, bring a full kettle of water to a boil, then measure out the desired amount.
1. Adjust oven rack to middle position and heat oven to 350 degrees. Grease two 9-inch or three 8-inch round cake pans, line with parchment paper, grease parchment, and flour pans. Whisk flour, baking soda, baking powder, and salt together in bowl. In second bowl, whisk boiling water, chocolate, cocoa, and espresso powder together until smooth.
2. Using stand mixer fitted with paddle, beat butter and sugar on medium-high speed until pale and fluffy, about 3 minutes. Add eggs, one at a time, and beat until combined. Add sour cream and vanilla and mix until incorporated.
3. Reduce speed to low and add flour mixture in 3 additions, alternating with chocolate mixture in 2 additions, scraping down bowl as needed. Give batter final stir by hand.
4. Divide batter evenly between prepared pans and smooth tops with rubber spatula. Bake until toothpick inserted in center comes out clean, 15 to 20 minutes (for 8-inch pans) or 25 to 30 minutes (for 9-inch pans), rotating pans halfway through baking.
5. Let cakes cool in pans on wire rack for 10 minutes. Remove cakes from pans, discarding parchment, and let cool completely on rack, about 2 hours.