In a mixing bowl, beat the mascarpone cheese, powdered sugar, and vanilla extract until combined.

Add the cold heavy cream and continue beating until the mixture becomes smooth and thick.

Divide the filling into two equal parts.

Dip the biscuits briefly in milk and arrange them in the bottom of a 15 x 15 cm baking dish.

Spread half of the mascarpone filling over the biscuit layer.

Slice the banana into rounds and arrange it over the filling. Add the raspberries and blueberries on top.

Spread the remaining mascarpone filling over the fruit layer.

Dip the remaining biscuits briefly in milk and place them on top.

Refrigerate the cake for 1 hour.

To make the ganache, heat the heavy cream until it just begins to boil.

Pour the hot cream over the broken chocolate and let it sit briefly.

Stir until smooth and glossy.

Pour the ganache over the chilled cake and spread evenly.

Return the cake to the refrigerator for another 2 hours.

Decorate with whipped cream, dried raspberries, or fresh fruit if desired, then slice and serve cold.