Chop chocolate into small pieces and place in a heatproof bowl. Heat cream and sugar until dissolved, then pour over chocolate and instant coffee granules. Whisk until smooth and chill for 30 minutes.

Preheat oven to 350°F (175°C). Grease two 9-inch round cake pans. In a bowl, whisk flour, cocoa powder, baking powder, baking soda, and salt. In another bowl, mix brown sugar, granulated sugar, eggs, oil, vanilla, and hot coffee. Combine wet and dry ingredients until just mixed.

Divide batter into the prepared pans and bake for 25-30 minutes, until a toothpick comes out clean. Cool in pans for 10 minutes before turning out onto a wire rack to cool completely.

To prepare coffee soak, mix boiling water and instant coffee granules until dissolved. Allow to cool. This will enhance the flavor of the cake layers.

Once the cakes are cool, slice each layer in half horizontally to create four layers. Brush the first layer with coffee soak, spread frosting, and repeat for the next two layers; place the final layer on top.

Apply a thin crumb coat of frosting over the cake and refrigerate for 15-20 minutes until set. This provides a smooth finish for the final frosting layer.

After the crumb coat is set, frost the top and sides of the cake with remaining frosting. Decorate as desired and serve.