For the grape strudel, beat the four yolks with 30 g granulated sugar, a pinch of cinnamon and the zest of an untreated lemon until foamy.
Beat two egg whites with 20 g granulated sugar until not too stiff and fold into the yolk mixture. Also stir in the grated nuts and the sponge crumbs.
Spread the filling in a third width on the finished strudel dough sheets and cover with grapes. Brush the remaining dough with melted butter and roll up the strudel. Also brush the outside with liquid butter and bake the grape strudel in a preheated oven at 210 ° C for 30-35 minutes.