I start by whisking the flour and salt together, then grating in cold butter straight from the fridge. Cold Greek yogurt, water, and buttermilk get mixed in just until the dough comes together. I flatten it into a rectangle, wrap it up, and chill it for 30 minutes before the first fold.
Once chilled, I roll the dough out on a well-floured surface and do one book fold, followed by three or four letter folds. I chill the dough for 30 minutes between each fold so the butter stays firm. This is what gives the pastry those flaky layers later on.
While the dough chills, I cook diced peaches with butter, brown sugar, maple syrup, cinnamon, and nutmeg in a saucepan until soft. A cornstarch slurry stirred in thickens everything into a jammy filling. I let it cool completely before using it, since warm filling melts the pastry butter.
I roll the chilled dough out and cut it into even rectangles. A heaping tablespoon of cooled filling goes in the center of half the rectangles, leaving a border around the edges. I brush the edges with egg wash, top with the second rectangle, and press and seal with a fork.
Each strudel gets brushed with egg wash and sprinkled with turbinado sugar before baking at 400°F for 18 to 22 minutes, until deeply golden and puffed. While they bake, I whisk together the maple vanilla glaze so it's ready the moment they come out.
I let the strudels cool for 5 to 10 minutes before drizzling on the glaze, since glazing too early makes it melt right off. Served warm with coffee, this is the moment all that chilling and folding pays off.