Prepare the Dough: Remove the refrigerated crescent dough from its packaging and unroll it onto a clean surface. Separate the dough along the perforated lines into 8 triangles. Keep the dough chilled until you are ready to shape it so it remains easy to handle.
Shape the Croissants: Starting at the wide end of each triangle, gently roll the dough toward the pointed tip. Place the pointed end underneath and curve the edges slightly inward to create a crescent shape.
Prepare the Egg Wash: In a small bowl, whisk together the egg and milk until smooth. This mixture will help the croissants develop a golden surface during cooking.
Brush with Butter: Lightly brush each shaped croissant with melted butter. If you prefer a slightly sweeter finish, mix the granulated sugar and vanilla extract into the melted butter before brushing.
Preheat the Air Fryer: Preheat the air fryer to 320°F for about 3 minutes, if your model requires preheating. Lightly grease the basket or use an air fryer-safe parchment liner.
Arrange the Croissants: Place the croissants in a single layer in the air fryer basket, leaving space between them for expansion. Brush the tops lightly with egg wash. Cook in batches if necessary.
Air Fry Until Golden: Air fry at 320°F for 8–12 minutes, checking around the 8-minute mark. Cook until the croissants are puffed and golden brown. Cooking time may vary depending on their size and your air fryer model.
Cool and Serve: Carefully remove the croissants from the basket and let them rest for 2–3 minutes. Dust with powdered sugar if desired and serve warm with your favorite spreads.