Mocha Cake with White and Dark Chocolate Ganache (Veludo Black and White)

For the dark chocolate ganache

200 g of dark chocolate, cut into pieces

2/3 cup (130 g) of unsalted butter, softened

2 tablespoons of coffee liqueur

1 tablespoon of unflavored gelatin, white

4 tablespoons of strong brewed coffee

1 cup of heavy cream (240 ml)

20 champagne or English biscuits

4 tablespoons of rum

For the white chocolate ganache

2 egg whites

4 tablespoons of unsalted butter, softened

170 g of white chocolate, cut into pieces

4 tablespoons of milk

1 tablespoon of unflavored gelatin, white

4 tablespoons of water

3/4 cup of heavy cream (180 ml)

For the topping

1/2 cup plus 1 tablespoon of water (135 ml)

1 cup of unsalted butter (180 g)

2 egg whites

2 tablespoons of dark chocolate, melted

Melted together with a whisk until smooth