For the cherry filling, bring the cherries up to a simmer with the sugar and cinnamon sticks, and simmer for 10 minutes. Whisk the cornstarch in a small bowl with a little cold water and add this to the cherries, stirring until the juices have thickened and the cherries are glossy. Set aside to cool before using.
For the strudel dough, blend the plain and bread flours with the salt in a mixer fitted with the paddle attachment. Add the water, oil and vinegar and mix on low speed until the dough comes together and then increase by one speed and knead for 2-3 minutes (the dough will seem sticky). Turn the dough out onto a lightly floured work surface and continue to knead the dough until it seems a smooth but elastic texture. Place the dough in a covered bowl and set aside to rest at room temperature for at least an hour.
To assemble, preheat the oven to 375 F. Lay a clean tablecloth out over your work surface and dust it evenly with flour. Place the strudel dough in the middle of the tablecloth and with your hands or a dusted rolling pin; spread the dough out as far as you can. Now switch to only using your hands (and keep them dusted with flour) and pull and stretch the dough from underneath, using the back of your hands, until it is almost transparent (it’s alright if a hole pops up here or there).
Once stretched as far as it can, brush the entire surface of the dough gently with butter (or spread it with your hand). Sprinkle the dough with breadcrumbs, then spoon the cool cherry filling over one end of the strudel. Trim away the end pieces of dough and, using the tablecloth for leverage, lift and roll up the strudel dough loosely and quickly. Use the tablecloth to lift it onto a parchment-lined baking tray (you can curve it, if it is bigger than the tray) and pinch the edges to ensure the strudel is sealed.
Brush the top with egg wash and bake for about 45 minutes, until it is a rich golden brown. Allow the strudel to cool for at least 20 minutes before slicing, and serve each slice generously dusted with icing sugar.
This strudel is best served the day it’s baked, but can be stored, refrigerated for up to 3 days.