Mix butter, milk, flour, sugar, yeast and egg to a smooth yeast dough. Let the dough rise until doubled in volume.
Once again knead the dough well by hand and roll it out.
For the filling, heat the milk and sugar and stir in the pudding powder. Spread the pudding on the dough, roll up the dough, place it on a baking tray and let it rise again for about 10 minutes.
Brush with milk and bake the strudel at 180 °C top/bottom heat for about 30 minutes.