Melt butter for the strudel dough. Knead 20 g melted butter, flour, salt, 2 tablespoons of oil, vanillin sugar and 150 ml of lukewarm water with the dough hooks of the hand mixer to a smooth dough (dough must be soft and elastic). Brush the dough with the remaining oil, wrap in foil and let it rest at room temperature for about 1 hour. In the meantime, wash the grapes, pluck them from the panicles and let them drain well. Mix the ricotta, egg yolks and bourbon vanilla sugar with the whisk of the hand mixer. Roll out the dough into a rectangle (60x55 cm) on a floured tea towel.
Cut off a 15 cm wide strip from the long side. Cut in half crosswise. Cut the remaining dough into four 15 cm long strips. Sprinkle breadcrumbs on each strip of dough. Spread ricotta cream on top, leaving a 2 cm wide edge all around. Spread grapes evenly on top. Roll up the four adjacent strips using the tea towel. Place on a baking tray lined with baking paper. Wrap the dough ends of each roll. Roll up the remaining strips of dough using the tea towel and place on the baking tray. Bake in a preheated oven (electric: 175 °C/ gas: level 2) for 50-60 minutes.
Spread grapes evenly on top. Roll up the four adjacent strips using the tea towel. Place on a baking tray lined with baking paper. Wrap the dough ends of each roll. Roll up the remaining strips of dough using the tea towel and place on the baking tray. Bake in a preheated oven (electric: 175 °C/ gas: level 2) for 50-60 minutes. After half of the baking time, brush the strudel with the remaining butter. Remove from the oven and serve lukewarm, dusted with icing sugar