Preheat the oven to 350°. Line the bottoms of 3-9” cake pans with parchment paper and lightly spray with baking spray. Set aside. In a large mixing bowl combine flour, cocoa powder, baking powder, salt and baking soda. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment combine sugar, butter and brown sugar. Add in the eggs, buttermilk and vanilla and mix on low speed to combine. Add in the flour mixture and mix until just incorporated. Scrape the sides of the bowl as needed. Mix in hot water and instant coffee.
Evenly divide the batter between the 3 prepared cake pans. Place the pans into the preheated oven on the center rack. Bake for 27 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs. Once baked, remove from the oven and place onto wire racks to let cool completely before frosting.
Make the buttercream:
In the bowl of a stand mixer fitted with a paddle attachment combine powdered sugar, butter, instant coffee, vanilla and salt. Beat on medium-high speed until smooth. (Note...if the buttercream is too thick, add milk or heavy cream one tablespoon at a time until it is the consistency you'd like.)
Assemble the cake:
Once the cakes have completely cooled, carefully remove them from the cake pans. Place the 1st cake onto a plate or cake stand. Add about 1 1⁄2 cup of frosting to the cake and evenly spread with an offset spatula. Place the 2nd cake on top and repeat the frosting process, ending with the 3rd cake on top.
Once all of the cakes have been layered, frost the top and sides of the cake. Using an icing spatula to get a smooth finish. Spoon the remaining frosting into a piping bag that is fitted with an open star tip. Pipe a border along the top and the bottom of the cake. Top with espresso beans.
Cake may be stored in an airtight container for up to 3 days.
*Use hot coffee in place of water for even more of a mocha flavor.Refer to the article above for more tips and tricks.The calories shown are based on the cake being cut into 15 pieces, with 1 serving being 1 slice of cake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information. The information in the nutrition box are calculated through a program and there is room for error. If you need an accurate count, I recommend running the ingredients through your favorite nutrition calculator.**