How to make a true apple strudel

It’s possible that, like me, your first encounter with the Grande Dame of the Austrian pastry world, the apfelstrudel, was not in fact in one of the famed Viennese grand cafés, but rather from the freezer aisle at the supermarket. If it was anything like mine, it was probably a latticed, puffed version; the one I remember from childhood had blackberries mixed into the apple, which peeked through the holes in the pastry.