01 - Dissolve yeast in warm milk with 1 teaspoon of sugar in a small bowl. Let sit for 5 minutes until foamy and activated.
02 - Mix flour, remaining sugar, and salt in a large bowl. Add melted butter, egg, and yeast mixture. Stir until combined, then knead for 5-8 minutes until smooth and elastic. Form into a ball, cover, and refrigerate for 1 hour.
03 - Place cold butter between two sheets of parchment paper. Pound and roll into a 6x6 inch square. Refrigerate until firm but pliable.
04 - On a floured surface, roll chilled dough into a 12x12 inch square. Place butter block at the center and fold dough edges over the butter, sealing completely to prevent leakage.
05 - Roll dough into a 16x8 inch rectangle. Fold into thirds like a letter. Turn 90 degrees, roll out again, and fold once more. Wrap and refrigerate for 30 minutes.
06 - Repeat rolling and folding process one more time. Wrap dough and refrigerate for another 30 minutes to rest gluten.
07 - Roll dough into a 16x10 inch rectangle. Cut into 8 triangles using a sharp knife or pizza cutter. Starting from the wide end, roll each triangle toward the tip to form classic crescent shape.
08 - Place shaped croissants on parchment-lined tray, cover loosely, and let rise in a warm place until puffy and doubled in size, about 1-2 hours.
09 - Preheat air fryer to 320°F. Brush risen croissants thoroughly with beaten egg for golden color.
10 - Place 2-4 croissants in air fryer basket without overcrowding. Air fry for 8-10 minutes until deep golden brown and fully cooked. Repeat with remaining batches.
11 - Let croissants cool on wire rack for 5-10 minutes before serving warm.