Preheat the oven to 350°F. Grease a 17×11 inch rimmed baking sheet and line with parchment paper.

In a medium saucepan, combine the butter, water, and cocoa. Heat over medium-low and whisk occasionally until the butter is melted and the mixture is smooth. Remove from heat and let cool until slightly warm, about 15 minutes.

In a mixing bowl, whisk together flour, brown sugar, espresso powder, baking soda, and salt. Make a well in the center.

In a large glass measure, whisk together the buttermilk, eggs, and vanilla. Add to the cooled chocolate mixture, whisking constantly. Pour the combined mixture into the dry ingredients and beat until smooth.

Pour the batter into the prepared pan, spreading evenly. Bake for 18-20 minutes or until a toothpick inserted in the center comes out clean. Let cool.

Freeze the cooled cake until firm, at least 30 minutes.

Invert the frozen cake onto a work surface and pull away the parchment paper. Trim into three 11×5 rectangles. Cover the layers with plastic wrap.

Place 1/2 cup of heavy cream and semisweet chocolate chips in a microwave-safe bowl. Heat for 1 minute, then whisk until a shiny ganache forms. Let cool for 10-15 minutes.

In a mixer, beat the remaining heavy cream until stiff peaks form. Fold whipped cream into the ganache until no streaks remain. Refrigerate.

In a mixer, beat cream cheese on high for 2 minutes. Add white chocolate and beat until smooth. Add butter and lemon juice; beat well. Add confectioners’ sugar and vanilla extract; mix until blended. Set aside.

Place one cake layer on a platter. Fill with chocolate mousse and spread evenly. Top with the second cake layer, add vanilla cream cheese filling, and spread evenly. Top with the final cake layer. Refrigerate.

For the ganache topping, heat chocolate chips, heavy cream, and oil in a microwave-safe bowl for 1 minute. Whisk until a shiny ganache forms.

For white glaze, whisk confectioners’ sugar and milk in a small bowl until combined. Adjust consistency with additional milk as needed.

Pour ganache over the top of the cake, spread carefully. Add lines of white glaze to the top and marble with a butter knife. Refrigerate.

For chocolate buttercream, mix butter, confectioners’ sugar, and cocoa powder. Add milk to thin to piping consistency. Beat until fluffy.

Pipe a large ‘S’ shaped scroll from one short end of the cake to the other. Arrange the wafer cookie in the center, with truffles around it. Refrigerate until ready to serve.