01 - Dissolve yeast in warm milk with 1 tsp of sugar. Let sit for 5 minutes until foamy.
02 - Mix flour, remaining sugar, and salt. Add melted butter, egg, and yeast mixture. Stir until combined, then knead for 5-8 minutes until smooth. Form into a ball, cover, and chill in the fridge for 1 hour.
03 - Place cold butter between two sheets of parchment paper. Pound and roll into a 6x6 inch square. Chill until firm.
04 - On a floured surface, roll dough into a 12x12 inch square. Place butter block at the center and fold the dough over the butter, sealing edges.
05 - Roll out into a 16x8 inch rectangle. Fold into thirds like a letter. Turn 90°, roll, and fold again. Wrap and chill for 30 minutes.
06 - Repeat rolling and folding one more time, then chill for another 30 minutes.
07 - Roll dough into a 16x10 inch rectangle. Cut into 8 triangles. Starting from the wide end, roll each triangle toward the tip to form a croissant.
08 - Place croissants on parchment-lined tray, cover, and let rise in a warm place until puffy (about 1-2 hours).
09 - Preheat air fryer to 320°F. Brush croissants with egg wash.
10 - Place 2-4 croissants in the air fryer basket without overcrowding. Air fry for 8-10 minutes or until golden and cooked through. Repeat with remaining croissants.
11 - Cool slightly before serving.