In the bowl of a stand mixer fitted with the paddle attachment, beat flour, cold butter, and salt at low speed just until butter is coated with flour. With mixer on low speed, add ⅔ cup (160 grams) ice water in a slow, steady stream, beating just until dough comes together, about 1 minute, stopping to scrape sides of bowl and turn dough to help dough hydrate evenly. (There will still be large pieces of butter. It is OK if a few dry bits remain). Turn out onto a lightly floured surface, and roll into a 9-inch square. Wrap in plastic wrap, and refrigerate for 45 minutes to 1 hour.
On a lightly floured surface, roll dough into an 18x10-inch rectangle, lightly flouring surface and top of dough as needed; fold dough in thirds, like a letter. Rotate dough 90 degrees; roll into an 18x10-inch rectangle, and fold into thirds, like a letter. Repeat procedure once more. Wrap dough in plastic wrap, and refrigerate for at least 1 hour.
Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.
On a lightly floured surface, roll dough into an 18½x16½-inch rectangle (about ⅛ inch thick). Trim edges to create an 18x16-inch rectangle. Cut into 24 (4x3-inch) rectangles. Place flat on prepared pan, and freeze until firm.
Place 12 rectangles at least 1 inch apart on pan. Spread 1½ tablespoons (33 grams) Pecan Pie Filling onto rectangles, leaving a ¼- to ½-inch border around edges. Brush all edges of dough with egg; top with remaining rectangles. Using the tines of a fork dipped in flour, seal edges. (Remove from pan to seal edges if it is easier to work with). Freeze until firm, 5 to 10 minutes.
Brush tops of dough with egg; sprinkle with sugar. Using a paring knife, score a small “X” onto the top of the dough.
Bake until sides look dry and tops and bottoms are a deep golden brown, 20 to 25 minutes. Let cool on pan for 10 minutes. Remove from pan, and let cool on a wire rack. Serve warm or at room temperature.
Recipe by Bake from Scratch at https://www.bakefromscratch.com/better-baking-academy-pecan-hand-pies/