In a small bowl, dissolve yeast in warm milk and let it sit for about 5 minutes.

In a mixing bowl, combine flour, sugar, and salt.

Add the yeast mixture to the dry ingredients and mix until a dough forms.

Knead the dough on a floured surface for about 10 minutes.

Shape the dough into a ball, cover it, and let it rise in a warm place for about 1 hour, or until doubled in size.

Roll out the cold butter between two sheets of parchment paper into a rectangle that is about 1 inch thick.

Roll out the dough into a large rectangle and place the butter layer in the center.

Fold the dough over the butter and seal the edges, then roll it out again.

Fold the dough into thirds, wrap it in plastic wrap, and chill for at least 30 minutes.

Repeat the rolling and folding process two more times.

After the final chill, roll the dough out and cut it into triangles.

Roll each triangle from the base to the tip to form croissants.

Place on a baking sheet, cover, and let rise for another hour.

Preheat the oven to 375°F (190°C).

Brush the croissants with egg wash and bake for 20-25 minutes, until golden brown.