Whip the cold cream with the sugar and vanilla until it holds stiff peaks.

Spread a thin layer of cream on one side of each biscuit and stand them in a row to form a long log.

Cover the whole log with the remaining cream and sprinkle the grated dark chocolate over it.

Wrap the covered log in plastic and chill for at least 4 hours, during which the biscuits soften into a cake-like texture.

Slice the rested log on the diagonal and serve.