Preheat the oven to 350 degrees. Grease two 9 × 2-inch round cake pans, line them with parchment paper, then grease and flour the pans. Set aside.
In the bowl of an electric mixer fitted with the paddle attachment, cream the butter and sugar on medium speed for 3 minutes, until light and fluffy. On low speed, add the eggs, one at a time. Add the vanilla and beat until well mixed, scraping down the bowl with a rubber spatula.
Whisk the cocoa powder and hot coffee together in a small bowl. With the mixer on low, add it into the batter.
In a medium bowl, sift together the flour, baking soda, baking powder, and salt. With the mixer on low, slowly add half the flour mixture to the batter, then all the sour cream, then the remaining flour mixture, mixing each addition until combined. With a rubber spatula, fold the batter until it is well mixed.
Divide the batter equally between the two prepared pans and smooth the tops. Bake for 30 to 35 minutes, until a toothpick inserted into the center comes out clean. Cool in the pans for 30 minutes, turn out onto a baking rack, and cool completely.
To frost the cakes, slice them in half horizontally with a long, thin knife (see note). Place the bottom of the first cake, cut side up, on a flat serving plate and spread a thin layer of buttercream on the top only (not the sides) with a palette knife. Place the top of the first cake, cut side down, on top and thinly frost the top only. Next, place the top layer of the second cake on top, cut side up, and thinly frost. Finally, place the bottom layer of the second cake, bottom side up (so the top of the cake is flat). Frost the top and sides of the cake.
Heat a palette knife or frosting spatula in hot water, shake off any excess water, and use it to smooth the buttercream on the sides and the top of the cake. Continue heating the palette knife and shaking off the excess water, until the buttercream is smooth. (A revolving cake stand will make it easier.) If there is extra buttercream, fill a pastry bag with it to decorate. Garnish with the chocolate espresso beans.
MAKE AHEAD Bake and frost the cake completely, cover with plastic wrap, and refrigerate for up to 3 days. Serve at room temperature.
Note: I use skewers and a long, thin flexible knife to cut the cakes evenly.
Coffee Meringue Buttercream:
Combine the sugar and 2⁄3 cup of water in a medium heavy-bottomed saucepan, cover, and bring to a boil over high heat. As soon as the sugar dissolves, uncover the pan and place a candy thermometer in the syrup. Cook over high heat until the thermometer registers exactly 240 degrees. (Don’t stir!)
Meanwhile, place the egg whites, cream of tartar, and salt in the bowl of an electric mixer fitted with the whisk attachment. Beat the egg whites on high speed until they form stiff peaks.
Carefully pour the syrup into a 2-cup glass measuring cup. With the mixer still on high, very slowly pour the sugar syrup into the egg whites in a thin, steady stream. Leave the mixer on high for about 1 hour (trust me!), until the mixture is completely at room temperature. (If the mixture isn’t absolutely at room temperature, the butter will melt and deflate the egg whites!)
With the mixer on medium, add the butter, 2 tablespoons at a time. If the butter starts to melt, stop and wait for the mixture to cool. With the mixer on low, add the coffee liqueur and vanilla. Do not refrigerate; frost the cake while the buttercream is at room temperature.
Reprinted from Cooking for Jeffrey. Copyright © 2016 by Ina Garten. Photographs by Quentin Bacon. Published by Clarkson Potter/Publishers, an imprint of Penguin Random House, LLC.