For the crumbles, mix flour, oat flakes, sugar, 1 pinch of salt, vanilla sugar, nuts, egg yolk, 3-4 tablespoons of cold water and butter in pieces in a mixing bowl with your hands to make crumbles.
Wash the apricots, remove the seeds and cut into slices. Stir the jam until smooth and mix carefully with the apricots. Just 2⁄3 Spread the crumbles evenly on a baking tray lined with baking paper.
Press to a floor with your hands. Sprinkle with breadcrumbs.
Spread the apricots on top. Spread the remaining crumbles evenly on top. Bake in the preheated oven (electric oven: 200 °C/circulating air: 175 °C/gas: see manufacturer) for approx. 45 minutes on the lowest rack. Dust the cake with icing sugar and let it cool down.
Whipped cream is delicious with it.