# How to Make It:
01 - In a large bowl, combine bread flour, sugar, and salt. Add cold milk, sourdough starter, and softened butter, mixing until just combined. Knead for approximately 8 minutes until the dough becomes smooth and elastic.
02 - Shape dough into a rectangle, wrap tightly in plastic wrap, and refrigerate for at least 2 hours.
03 - Place cold butter between two sheets of parchment paper. Pound and roll into an 8 by 6 inch rectangle. Chill until firm but pliable.
04 - On a lightly floured surface, roll dough to a 16 by 8 inch rectangle. Position butter block on one half, fold dough over the butter, and seal all edges firmly.
05 - Turn dough 90 degrees and roll into a 24 by 8 inch rectangle. Fold into thirds using a letter fold method, wrap in plastic, and chill for 1 hour.
06 - Repeat the rolling, folding, and chilling process two additional times, allowing 1 hour of rest between each turn.
07 - After the final fold, wrap dough carefully and refrigerate overnight for 8 to 12 hours.
08 - The following morning, roll chilled dough into a 24 by 12 inch rectangle approximately 1/4 inch thick. Cut into 12 long triangles using a sharp knife.
09 - Starting from the wide end of each triangle, tightly roll toward the point, then bend into a crescent shape and tuck the tip underneath. Place on parchment paper-lined baking sheets.
10 - Cover loosely with cloth and allow croissants to proof at room temperature until doubled in size, approximately 2 to 3 hours.
11 - Preheat oven to 400°F (200°C).
12 - Whisk together egg and milk. Brush mixture lightly and evenly over each croissant.
13 - Bake for 18 to 22 minutes until croissants are golden brown and crisp. Cool slightly before serving.