Put the flour, powdered sugar, salt, butter and egg in a mixing bowl. Pour in the yeast-milk mixture slowly and knead everything together to form a smooth dough. Cover and let rise to double volume in a warm place.
In the meantime, mix the curd cheese, egg, powdered sugar and custard powder together well for the filling.
If you use canned apricots, put them in a sieve and drain well. Dip fresh apricots briefly in boiling water, then rinse with cold water and peel off the skin. Then cut the apricots into small cubes.
Roll out the risen yeast dough on a lightly floured work surface into an approx. 30 x 40 cm rectangle. Brush with the curd cheese filling (leaving a small edge all around) and then sprinkle with the apricot cubes. Roll up carefully from the long side and press the ends together well. Line a baking sheet with parchment paper and place the strudel on top with the seam down. Cover and let rise for another 30 minutes.
Beat the egg with milk and brush the strudel with it.
Bake in the preheated oven at 180 ° C for about 30 minutes.