Steps
1. In a bowl, mix flour, sugar, salt, and yeast.
2. Add warm milk and cold butter for dough; mix until combined.
3. Knead gently and form into a ball; refrigerate for 30 minutes.
4. Roll out dough into a rectangle, place cold butter slab in the center, fold dough over butter.
5. Roll out and fold dough into thirds (letter fold). Refrigerate 30 minutes.
6. Repeat rolling and folding two more times, chilling between each.
7. Roll dough into a large rectangle, cut into triangles.
8. Roll each triangle from base to tip, shape into croissants.
9. Place croissants on baking tray, cover, and proof for 1-2 hours until doubled.
10. Preheat oven to 200°C (390°F).
11. Brush croissants with beaten egg.
12. Bake for 15-20 minutes until golden brown and flaky.
13. Cool slightly before serving.