Preheat the oven to 350F/177C. Line two, 8-inch (20-cm) round cake pans with parchment paper; leave the sides ungreased.

Prepare the cake batter first. Place the eggs, sugar and vanilla into a stand mixer bowl and whisk on high speed for 7 to 8 minutes, until the eggs are voluminous and pale in color. In a separate bowl, combine the flour and baking powder. Sift the dry ingredients into the batter in small amounts, folding gently but thoroughly after each addition. Scrape from the bottom of the bowl to incorporate.

Next, add the melted butter and instant coffee granules; fold in gently. Divide the batter evenly between the two pans. Bake the layers in the preheated oven for 22 to 25 minutes, until the top of the cakes are golden brown and spring back when pressed lightly in the center. Remove the layers from the oven and run a knife along the edge to release the cake from the sides, then cool completely on a wire rack. Once cooled, use a long, serrated knife to slice each layer in half.

Prepare the filling while the layers are baking and cooling. In a small saucepan, combine the dried prunes, coffee, brandy and orange juice. Bring the mixture up to a simmer and cook over medium heat for 12 to 15 minutes, until the mixture is thicken significantly. Allow the filling to cool before using in the cake.

Prepare the chantilly cream when ready to assemble the cake. In a large mixing bowl, whisk the chilled heavy cream and vanilla on medium speed and gradually add in the confectioner's sugar. Add 2 cups for a less sweet version. Once all the sugar is added, whisk on high speed for 3 to 4 minutes, until stiff peaks form. Transfer about 1/3 of the whipped cream into a pastry bag tipped with a simple round tip or open French star tip.

For the soaking syrup, simply combine the brandy and coffee in a dispenser bottle, or in a small bowl and use a pastry brush for soaking.

To assemble the cake, first soak each layer generously with the syrup, then spread about 1/4 cup dulce de leche onto the layer. Pipe a barrier border around the edge of the cake, then fill the center with 1/3 of the filling for each layer. Spread the prune filling to the edges, then top with the whipped cream. Frost the top and sides of the cake with the remaining cream.

To garnish the sides of the cake, use a peeler and shave off pieces of chocolate off of a chocolate bar. Press the shaved chocolate gently into the sides. Garnish the top with dollops of whipped cream and chocolate pieces, if desired. Allow the cake to set in the refrigerator for a few hours before serving.