Place the prunes in a medium-sized bowl and pour the coffee over top. Set the prunes aside to soak for 30 minutes.
Use a double boiler to melt the chocolate and butter. Stir the chocolate and butter occasionally until they melt and form a cohesive mixture.
Beat the eggs, yolks, and sugar together until frothy. When the chocolate has melted, pour it into the egg mixture. Stir in the coffee-soaked prunes.
In a separate bowl, place the flour and add the salt and espresso powder. Sift in the black cocoa. Fold the flour mixture into the chocolate.
Place the cream cheese in a bowl. Sift in the powdered sugar, and beat until fluffy. Add the white chocolate to the cream cheese mixture. Slowly stream in the coffee.
Take the set mousse out of the fridge and whisk it to loosen it up. Pile the mousse on top of the cake and create a series of pleasing swoops.
Top the cake with the chocolate-covered espresso beans and finish with a dusting of gold luster, if desired.