Melt the butter. Finely mash the sponge finger. Knead well with the butter. Place a springform pan rim (26 cm Ø) on a cake plate. Spread the crumb mixture in the ring, press it firmly and chill.
Wash the currants, drain them and remove them from the panicles with a fork. Wash and stone the cherries. Scald peaches briefly with boiling water, rinse with cold water and peel the skin.
Cut peaches in half, remove stones and cut halves into thin slices. Soak gelatine in plenty of cold water. Wash the lime hot. Peel the skin thinly and cut into fine strips.
Squeeze the juice. Mix yoghurt, sugar, vanillin sugar and lime juice. Squeeze the gelatine, dissolve at low heat and stir into the yoghurt cream. Put the mixture in a cool place. Whip cream until stiff.
As soon as the yoghurt cream begins to set, fold in the cream and 2/3 of the mixed fruit. Spread the cream on the crumb base. Sprinkle with the remaining fruits and press them gently into the cream.
Put the cake in a cool place for about 3 hours. Then carefully loosen the cake edge and serve the cake sprinkled with the lime zest.