Make the cake mix. Use a fine mesh sieve to sift flour, cocoa powder, baking powder and baking soda into a large bowl. Add sugar and salt and whisk to blend very well so the ingredients are evenly combined.

Preheat oven to 350°F. Lightly grease two 8-inch round cake pans, dust lightly with flour and line the base with rounds of parchment paper.

First prepare the coffee and keep it hot. If you are using instant coffee, add 1 tablespoon of instant coffee granules or 2 teaspoons of espresso powder to 1 cup of just boiled water and set it aside while you prepare the batter.

Combine eggs, oil, sour cream and vanilla in a medium bowl and whisk to blend well. Pour into the bowl with the dry ingredients and mix with an electric handheld mixer on medium-low until blended.

Add the hot coffee gradually in two stages to minimize clumps forming and mix until evenly combined and the batter is smooth.

Divide batter evenly between the prepared pans and tap the pans on the countertop to allow any large air bubbles to surface and pop.

Bake for 30-33 minutes until cakes spring back when pressed gently and a skewer inserted into the center comes out clean.

Transfer pans to a wire rack and let cool for 15 minutes before running a knife or offset spatula around the sides and inverting the cakes onto the rack to cool completely.

Assemble the cake. Once cakes are cooled, place one cake layer on a serving plate. Spread about ¾ cup of frosting over the top, then place the other cake layer on top. Cover the entire cake with frosting