Unroll the puff pastry, cut off approx. 13 cm from the long side. Line a tart mould (bottom 22 cm Ø, top 26 cm Ø, height 3.5 cm) with parchment paper. Place large strips of dough in the middle of the tin. Cut small strips in half lengthwise and press them against the two long sides of the dough in the mould. Put the dough in a cool place. Wash the grapes, dab dry and pluck off the stalks.
Mix sour cream, 2 tbsp. sugar, eggs and pudding powder. Sprinkle puff pastry with ground hazelnuts. Spread the grapes on top and pour the icing over it. Spread the edge of the pastry with milk. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 30-40 minutes. In the meantime, melt 1 tbsp. sugar in a pan and stir in the hazelnut flakes. Pour onto baking paper and allow to cool. Take the cake out of the oven and let it cool down. Lift out of the pan and arrange on a plate.
Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 30-40 minutes. In the meantime, melt 1 tbsp. sugar in a pan and stir in the hazelnut flakes. Pour onto baking paper and allow to cool. Take the cake out of the oven and let it cool down. Lift out of the pan and arrange on a plate. Crumble the brittle and sprinkle on the tart. Sprinkle with icing sugar
waiting time 1 1/2 hours