Roast the hazelnut leaves in a pan without fat until golden brown. Leave to cool. Mix curd and sugar with the whisk of the hand mixer. Whip the cream until stiff, allowing the vanilla sugar to trickle in.
Fold the cream under the quark. Melt the nut nougat cream slightly in a hot water bath and fold into the quark cream as streaks. Pour Nutella quark cream into dessert glasses and serve sprinkled with hazelnut leaves.