Put the pitted cherries in a small pot, pour 3 1/3 tbsp (50 g) of sugar over them and the juice of 1 lemon. Put the container on moderate heat and boil the fruits for 10 min. Take off the stove and cool.
Soak the gelatin in cold water until softened. Heat the milk, add the softened gelatin and stir until it melts.
Pour the yoghurt in a large bowl, add the milk with gelatin, flavor with a vanilla and 1/3 cup (80 g) sugar.
Beat the well cooled cream to hard snow. Add it in portions to the yoghurt while stirring energetically until you obtain a smooth, homogeneous mixture.
Pour the resulting cream into a rectangular cake form. Arrange the cherries on top and cover with biscotti. Cover the form with plastic wrap and put it in the fridge.
Leave the dessert overnight to harden well.
To take the dessert out of the form, dip it in warm water for 2-3 min. Invert it onto a suitable plate.