For the yeast dough apple strudel, first prepare the filling. Melt the butter, toast the breadcrumbs in it and set aside to cool.
Peel and core the apples and slice them thinly with a food processor. Mix the cinnamon, lemon zest and rum into the apples. Now take the 4 strudels out of the package, roll them out and coat them with the butter and breadcrumb mixture.
Put 1/4 of the apple mixture on each strudel and sprinkle with sugar. Carefully remove the dough from the backing paper and fold over the apples. Place seam side down on a baking sheet.
Whisk the egg with the milk and brush the strudels with it. Finally, prick the surface of the yeast dough apple strudel with a baking pin and bake in the preheated oven at 175 °C for about 35 minutes until golden brown.