1. Whisk together flour, powdered sugar, cinnamon, and salt.
2. Add cold butter; mix until coarse crumbs form.
3. Drizzle in cold milk; mix until a shaggy dough forms.
4. Wrap dough in plastic; chill 30 minutes.
5. Whisk pumpkin puree, egg yolks, brown sugar, vanilla, spices, cornstarch, and salt until smooth.
6. Roll chilled dough to ⅛-inch thickness; cut into circles.
7. Place 2 tablespoons of filling on each circle, leaving a ½-inch border.
8. Brush edges with egg, fold, and crimp.
9. Brush tops with egg wash; cut steam vents.
10. Bake at 375°F for 20-25 minutes until golden brown.