Beat the cream with the sugar in a deep bowl. Add the mascarpone and beat.
Pour a little milk in a deep plate. Dip the biscuits in it and arrange 1/2 of them in a square form. Put a layer of chocolate spread on top and spread it out with a spoon.
Pour on half the cream and arrange another layer of biscuits. Smear with a layer of chocolate and spread out the remaining cream on top.
Decorate with chocolate spread or cocoa if desired. Leave in the fridge for about 24 hours before serving.