Prepare the mixture for the spherification a day in advance: in a saucepan, mix the water and sugar and bring to the boil. Break the chocolate in to pieces. Once the sugar syrup is boiling, pour it over the chocolate and then add the amaretto, mix well. Mix 200ml of this liquid with the sodium alginate using an electric whisk or blender. Cover and leave to rest at room temperature for at least 12 hours, this will get rid of any air bubbles.
Mix the mineral water and the calcium with a whisk to make the 'cooking' bath.
Fill a syringue with the chocolate mixture and then use a measuring spoon to make 'marbles' of chocolate. Gently place these marbles in to the calcium bath and allow to 'cook' for 5 minutes. Remove from the calcium bath and rinse under cold water.
To make the tiramisu: soak the sponge fingers in the coffee. Whisk the egg yolks and the sugar until the mixture is pale and fluffy. Mix in the mascarpone. Whip the cream then fold in the beaten egg yolks. Carefully place the sponge fingers in the base of individual bodega ramekins. Cover the sponge base with the mascarpone and then chill.
To serve, top the tiramisu with the chocolate 'marbles'.
«Make sure to rinse the chocolate 'marbles' after the spherification process.»