To Make the Pastry:

1. In a medium-sized bowl, stir together flour and salt. Cut butter into flour until the mixture is crumbly, not fine. 
2. In a separate bowl, whisk together 1/4 cup water and egg yolk. Add the wet ingredients to the flour mixture and stir to combine with a fork. Knead the dough right in the bowl for a couple seconds until smooth.
3. Form the dough into a ball. If you wish, wrap in plastic wrap and refrigerate until ready to use. At least 4 hours is suggested when working in a hot kitchen, or up to 8 hours/overnight. 

To Make the Filling:

1. Combine all filling ingredients except the butter and powdered sugar in a bowl. Toss well to coat the apples.
2. Filling can be made a day ahead and refrigerated until ready to use.

To Make the Strudel:

1. Preheat oven to 400˚F.
2. Set a piece of parchment paper that fits within a rimmed baking sheet on the counter and flour it lightly. Set dough on top, and flour it lightly. Place another piece of parchment on top of the dough.
3. Roll the dough out as thinly as you can, sandwiched between the parchment, so it forms a rectangle longer in length than width, about 9 inches by 14 inches. If the dough is sticking, add flour. If it’s too cold to work with, let it sit on the counter for 15-30 minutes, until more pliable. 
4. Place the filling in a mound in a straight line along the length of your dough. This should be like a mountain with no peaks, all uniform, pressed together compactly, about 1 1/2 to 2 inches high (see picture above for a rough idea). Dot with butter on top.
5. Carefully roll parchment on sides up and over the filling, one side at a time, peeling parchment back from dough after you’ve set it. Then roll up the ends. Gently press together the seams. 
6. Transfer the dough with the bottom parchment to a rimmed baking sheet. 
7. In a small bowl, beat together 1 egg and 2 teaspoons cold water to make an egg wash. Brush all over the pastry. Use a fork to pierce air vents along the sides of the strudel. Bake for 30 minutes, until golden and fragrant.
8. Sprinkle with powdered sugar and serve warm.