Preheat your oven to 350°F (175°C) and prepare two 9-inch round cake pans by greasing them with butter or lining with parchment paper.

In a medium saucepan over medium heat, melt together the unsalted butter, water, and unsweetened dark cocoa powder. Stir constantly until smooth and glossy, about 3-5 minutes.

In a large mixing bowl, whisk together the all-purpose flour, light brown sugar, espresso powder, baking soda, and fine grain sea salt.

Pour the chocolate mixture into the bowl of dry ingredients. Add buttermilk, large eggs, and vanilla extract, stirring until just combined.

Divide the batter evenly between the prepared pans, smoothing the tops. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.

Once baked, remove the cakes from the oven and let them cool in the pans for about 10 minutes, then transfer to wire racks to cool completely.

In a chilled mixing bowl, whip the heavy cream until stiff peaks form, then fold in the semisweet chocolate chips.

In another mixing bowl, combine cream cheese, melted white chocolate, softened butter, lemon juice, confectioners’ sugar, and vanilla extract. Beat until smooth.

Place one chocolate cake layer on a serving platter. Spread mousse evenly on top followed by a layer of the cream cheese mixture. Repeat with the second layer.

In a small saucepan, combine semisweet chocolate chips, heavy cream, and sunflower oil over low heat. Stir until melted and smooth.

Pour the warm ganache over the top of the assembled cake, allowing it to drip down the sides. Use a spatula to guide it if needed.

Finish with decorative touches like chocolate truffles or rolled cookie wafers on top.