Prepare the frosting by combining dark and semi-sweet chocolate with instant coffee granules. Heat heavy cream and sugar until the sugar dissolves, then pour it over the chocolate and whisk until smooth. Chill in the refrigerator for 30 minutes.

Preheat oven to 350°F (175°C) and grease two 9-inch round pans. Whisk together flour, cocoa powder, baking powder, baking soda, and salt in a large bowl. In another bowl, mix eggs, granulated sugar, dark brown sugar, oil, vanilla, and hot coffee until combined. Fold dry ingredients into wet ingredients until smooth.

Divide batter between prepared pans and bake for 25-30 minutes or until a toothpick comes out clean. Cool in pans for 10 minutes before transferring to a wire rack to cool completely.

Prepare coffee soak by whisking hot water and remaining instant coffee granules until dissolved. Let cool to room temperature.

Once the cakes are cool, slice each layer in half horizontally, creating four layers. Brush each layer with coffee soak, then spread chilled frosting on top, repeating for each layer.

Apply a crumb coat with a thin layer of frosting over the entire cake and chill for 15-20 minutes to set.

Smooth a final layer of frosting over the cake and decorate as desired. Serve and enjoy!