In a bowl, mix warm milk and yeast. Let it sit for 5 minutes until foamy.
In a separate bowl, combine flour, sugar, and salt.
Create a well in the center of the dry ingredients and add the yeast mixture.
Mix until a rough dough forms and knead for 5 minutes.
Wrap the dough in plastic wrap and refrigerate for 1 hour.
Roll out the cold butter between two sheets of parchment paper into a rectangle.
Roll the dough into a larger rectangle and place the butter in the center.
Fold the dough over the butter, sealing the edges.
Roll the dough out again and perform a series of folds (3 folds total).
Chill the dough for 30 minutes after each fold.
Roll out and cut into triangles, then roll them up to form croissants.
Let them rise for 1-2 hours before baking at 400°F (200°C) for 20-25 minutes.