Cake base (Perfect All-American Chocolate Butter Cake from The Cake Bible)
1/2 cup + 3 Tbs unsweetened cocoa
1 cup boiling water
3 large eggs
2 1/4 tsp vanilla
2 1/4 cups + 2Tbs sifted cake flour (note, measure AFTER sifting)
1 1/2 cups sugar
1 Tbs baking powder
3/4 tsp salt
1 cup unsalted butter (softened)

• Preheat oven to 350
• Whisk cocoa and boiling water until smooth, cool
• In another bowl lightly combine eggs, 1/4 cocoa mixture, vanilla
• In another bowl, combine remaining dry ingredients, mix on low for 30 sec
• Add butter and remaining cocoa mixture, mix on low until moistened
• Increase to medium, beat 1 1/2 min, scrape down sides
• Gradually add egg mixture in 3 batches, beat for 20 sec after each addition, scrape down sides
• Scrape batter into two 9 inch by 1 1/2 inch cake pans, greased, bottoms lined with parchment or wax paper, then greased and floured
• Bake 25-35 min or until tester comes out clean
• Let cool in pan 10 min, then invert onto wire racks and cool completely
  
• Pour about 1/4 cup of Kahlua into cakes and let them absorb the liquid

Mocha buttercream
6 large egg yolks
1/4 cup sugar
1/2 cup corn syrup
2 cups unsalted, softened butter
6 oz melted and cooled bittersweet chocolate
2 Tbs instant espresso powder dissolved in 1 Tbs boiling water