Note "00" flour has a higher gluten content than plain flour and makes a more elastic dough. If it's unavailable, substitute plain flour.
The earliest known written recipe for strudel, dating from 1696, is regarded in Austria as a national treasure, and it's kept under lock and key at the City and State Library of Vienna.
Food historian Charles Perry speculates that fillo, the paper-thin pastry that defines strudel as well as closely related pastries such as baklava, was invented in Istanbul under the Ottoman empire around 1500. Under Suleiman the Magnificent, the empire expanded to reach the gates of Vienna, taking fillo with it. The pastry itself, and the desserts made with it, became known in Austria as strudel and in Hungary as rétes.
In German, the word "strudel" means vortex or whirlpool, referring to the way the pastry is rolled around a filling to form many layers. Apples are the most popular filling in Western Europe today, especially in Austria, while in the Balkans, cherries are a particular favourite. And that original 1696 recipe? It's for Milchrahmstrudel, filled with milk-based custard.
Strudel dough's defining quality is its thinness. Stretching the dough without breaking it is a skill that takes time and patience to perfect. A kitchen table or island bench is a big help, because it will allow you to walk around the dough and stretch it from all sides. When it's thin enough, you should be able to read this text through it. At this point, use a pastry brush and a flicking action to cover the dough with melted butter (brushing the butter on directly can snag and tear the dough). Don't worry, though, if your dough has a few small holes - the results will still taste delicious.