In another bowl, break the chocolate and add the butter in. Place on a double boiler and bring to melt. Add in the sweetened condenced milk, as well as the fresh cream and whisk well to obtain a smooth ganache.
Pour the chocolate ganache onto the biscuits and coat well.
Pour the cake mix into a plastic or parchement lined pan and press down with a spoon.
Cover with foil paper and store in the freezer for at least 6 hours before serving.
Remove from the freezer and dust with some cocoa powder before serving. You can also decorate with some whip cream and crushed hazelnut.
I recommend placing a layer of either parchment, wax paper, or a plastic food wrap in the cake pan before adding the batter. This makes it easier to remove the cake because it gets sticky.
You can use any shape of pan you like. You can use two smaller pans to make the portion into two batches, freeze and serve whenever you like.
Another way to make this cake. Simply just scoop the mix onto plastic wrap and wrap it into a roll shape and freeze it. When you are ready to serve, just take it out of the freezer and cut it into pieces and serve.