Preheat oven to 350°F (175°C). Mix dry ingredients, add wet ingredients, and combine. Bake for 45 minutes.
Prepare frosting by beating cream cheese and butter, then gradually add powdered sugar and cocoa. Mix in espresso powder, vanilla, and buttermilk until smooth.
Allow cake to cool, then spread frosting evenly over the top and sides.
Notes
For best results, use high-quality cocoa and fresh ingredients.