Pour the cherries into a sieve and drain well. Then sprinkle the cherries with sherry. Crumble the sponge finger roughly. Whip the sour cream with the whisks of the hand mixer, adding vanilla sugar and sugar. Add yoghurt and stir in. Layer crumbled lady fingers, soaked sherry cherries and cream in 4 dessert glasses. Mix cocoa and icing sugar and dust the cream with it
Serve decorated with lemon balm as desired