Melt butter. Finely crumble the shortbread biscuits and mix well with the liquid butter. Place a springform rim (26 cm diameter) on a cake plate and press the biscuit crumbs into the mold as a smooth base. Chill for about 30 minutes.
In the meantime, soak the gelatine in cold water for about 10 minutes. Put the yogurt in a bowl. Squeeze out the gelatine, dissolve it and mix it with 2-3 tablespoons of yoghurt. Then stir in the rest of the yogurt. Chill for about 10 minutes.
When the yoghurt starts to gel, pour the mixture onto the shortbread base and smooth it out. Chill the cake for at least 4 hours, preferably overnight.
Wash the nectarine, pat dry, cut in half and remove the stone. Cut halves into wedges. Remove the cake from the springform rim with a knife and decorate with nectarines and shortbread minis.