01 - Whisk together flour, salt, and sugar in a large bowl until evenly combined.
02 - Add cold butter cubes. Use a pastry cutter or fingertips to work butter into flour until mixture resembles coarse crumbs with some pea-sized pieces remaining.
03 - Gradually drizzle in ice water while mixing gently. Stop when dough just begins to hold together. Divide into two equal portions, shape into discs, wrap tightly, and refrigerate for at least 1 hour.
04 - Roll out one dough disc on a lightly floured surface to approximately 12 inches in diameter. Carefully transfer to a 9-inch pie plate, pressing gently into bottom and up the sides. Trim edges even with rim. Refrigerate while preparing braids.
05 - Roll out second dough disc to 1/4 inch thickness. Using a sharp knife or pastry wheel, cut twelve long strips approximately 1/2 inch wide and 8-10 inches long.
06 - Group strips into three sets of four. Pinch tops of each set together to secure. For each set: position strips left to right as 1-2-3-4. Cross strip 1 over strip 2, under strip 3, over strip 4. Repeat with the new leftmost strip each time until fully braided. Pinch bottom end to seal.
07 - Carefully transfer braids along the chilled pie crust edge, pressing gently to adhere. Trim any excess length. Lightly brush crust edge with water to help seal braids in place if necessary.
08 - Refrigerate assembled pie for 15 minutes to firm the dough. Meanwhile, preheat oven to 400°F.
09 - Whisk together beaten egg and milk. Brush evenly over braided crust using a pastry brush.
10 - Line crust with parchment paper and fill with pie weights or dried beans. Bake for 12-15 minutes until lightly golden. Remove parchment and weights. Continue baking for 3-5 additional minutes if bottom needs crisping.
11 - Proceed with filling and baking according to your chosen pie recipe, or cool completely if using as a pre-baked shell.