Peel, quarter and core the apples. Cut the flesh into slices and sprinkle with lemon juice. Knead ground nuts, flour, butter, sugar and vanilla sugar until crumbly. Grease four small soufflé bowls and spread apple slices on top.
Cover with the nut crumbles and bake in the preheated oven (electric oven: 175° C/ gas: level 2) in the lowest third for approx. 40 minutes. Coarsely chop the hazelnut kernels and sprinkle them on crumbles shortly before serving.
Decorate with apple slices and lemon balm as desired. Vanilla sauce tastes good with it.