In a large mixing bowl, combine all-purpose flour, sugar, and salt. In a separate bowl, dissolve yeast in warm milk. Let sit for 5 minutes until foamy. Add to dry ingredients with melted butter, mixing until smooth. Knead for 3-5 minutes, wrap, and refrigerate for 1 hour.

Prepare the butter block by rolling cold unsalted butter between parchment sheets into a 6-inch square. Keep it cold.

Roll chilled dough into a 12-inch square, place the butter block in the center, and fold corners over butter to encase it. Roll into an 8"x20" rectangle, fold into thirds like a letter, wrap in plastic, and chill for 30 minutes.

Repeat lamination by rolling into another 8"x20" rectangle, folding into thirds, and refrigerating for another 30 minutes. Repeat this process 3 times in total.

After the final turn, roll the dough to 1/4 inch thick and cut into triangles. Roll each triangle from the wide end towards the tip, tucking the point underneath.

Place croissants on a parchment-lined baking sheet, cover with a towel, and allow them to rise at room temperature for 1.5 to 2 hours.

Preheat the oven to 400°F (200°C). Brush croissants with egg wash and bake for 18-22 minutes until golden brown.

Let baked croissants cool on a wire rack to maintain flakiness before indulging.