In a medium saucepan, heat heavy cream and granulated sugar over medium heat, stirring until the sugar dissolves.

Remove from heat and add chopped dark chocolate and vanilla extract; whisk until smooth.

Cool in the refrigerator for about 1 hour, allowing the frosting to thicken.

Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans.

In a large mixing bowl, whisk together flour, granulated sugar, dark brown sugar, cocoa powder, baking powder, baking soda, and salt.

In a separate bowl, combine eggs, butter, vanilla extract, and hot brewed coffee.

Mix all wet ingredients with dry until fully incorporated.

Pour the cake batter evenly into the prepared pans and smooth the tops.

Bake in the preheated oven for 30-35 minutes.

Cool in the pans for 10 minutes before transferring to a wire rack.

In a small bowl, whisk together instant coffee with hot water and melted dark chocolate until fully dissolved.

Let cool to room temperature.

Once cooled, carefully level the tops of the cakes.

Slice each cake in half horizontally to create four layers.

Brush one layer with coffee soak and spread frosting over it; repeat with other layers.

Apply a thin layer of frosting over the entire cake to seal in crumbs.

Refrigerate for 20-30 minutes to set the crumb coat.

Use remaining frosting to cover the top and sides of the cake.

Smooth with a spatula or cake scraper.