• In a mixing bowl beat the butter and sifted sugar until you get a pale and fluffy cream.
• Add the yolk (if using) and incorporate it well into the mixture.
• Add the whey-free cream gradually until you get a homogeneous mixture and reserve.
• Add 1 tablespoon of port wine or liquor, if using mix well and set aside while we prepare the base.

For the cookie base:

• Prepare a deep dish with milk and a springform cake pan.
• Dip the cornstarch biscuits in the milk and arrange them in a layer at the bottom of the pan. You can also place some along the edge to form an upward crust.
• Divide the cream in 3 parts and spread 1/3 of it into an even layer. Follow with another layer of moistened biscuits and the next third of the cream, alternating in this way until you finish with a final layer of biscuits.
• Cover the pan with plastic film and place in the fridge until firm (at least 5 hours or overnight would be best).

For the chocolate ganache:

• Once set, it's time to prepare the chocolate topping. To do this, heat up the heavy cream in a saucepan on medium-low heat until it begins to bubble. Remove from the heat and stir in the chocolate powder, and butter and continue stirring until it thickens. Set aside to cool.
• Pour the chocolate ganache over the cake and serve cold.

Enjoy!