Tip: If the butter begins to soften from handling, place it in the freezer for about 10 minutes. Keeping the butter cold is essential for a flaky crust—the small frozen pieces create steam in the oven, helping the layers puff up beautifully.
Step 2: Add Liquid and Chill
Pour the ice water into the center of the mixture. Use a fork to combine until a shaggy dough forms. Add additional water, one tablespoon at a time, until the dough holds together without becoming sticky. Divide into two portions, shape into rectangles, wrap, and refrigerate for at least 30 minutes.
Step 3: Assemble the Layers
Preheat the oven to 400°F. Roll out one portion of dough to fit a 9×13-inch jelly roll pan and press it into place. Evenly spread the apple filling over the crust. Roll out the second portion of dough and place it over the filling, sealing the edges by pinching them together.
Step 4: Bake and Vent
Cut a few small slits in the top crust to allow steam to escape. Bake for about 40 minutes, rotating the pan halfway through, until the crust turns a deep golden brown. Allow it to cool completely on a wire rack.
Step 5: Add the Glaze
In a bowl, mix the powdered sugar, softened butter, vanilla, and milk until smooth. Spread the glaze evenly over the cooled pastry. Let it set for about 20 minutes before cutting into squares.
