Preheat your oven to 350°F (175°C). Grease two 9-inch round cake pans with butter or line with parchment paper.

In a medium saucepan, combine unsalted butter, water, and unsweet dark cocoa powder over low heat. Stir until melted and smooth, then cool slightly.

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

Add the cooled butter-cocoa mixture to the dry ingredients and mix gently until just combined.

Incorporate buttermilk, eggs, and vanilla extract, mixing until smooth and velvety.

Divide the batter between the prepared pans and bake for 30-35 minutes until a toothpick comes out clean.

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

Whip heavy cream until stiff peaks form, about 3-5 minutes.

Blend cream cheese, melted white chocolate, confectioners' sugar, and softened butter until smooth. Optionally, add lemon juice.

Layer one cake, half of whipped cream, and half of cream cheese mixture. Top with the second cake layer and repeat.

For ganache, combine semisweet chocolate chips, heavy cream, and sunflower oil in a microwave-safe bowl. Heat in 30-second increments until smooth.

Pour ganache over the cake and let it drip down the sides.

Decorate with piped frosting, rolled cookie wafers, and chocolate truffles.