Combine the mascarpone with the cream and the yolks. Whip at speed 6 using a mixer. Whisk the egg whites until stiff, gradually adding the sugar. Combine the 2 mixtures.
Position a circle of sponge finger that has been soaked with strong coffee syrup in a ring mould. Add the tiramisù mixture and smooth. Add a second soaked sponge finger circle and pipe on different sized dots of the tiramisù mixture using a piping bag (n°8 plain nozzle). Sprinkle over the cocoa powder and serve chilled.