Preheat your air fryer to 325°F (160°C). Lightly spray the basket with nonstick spray or line with perforated parchment paper.
Unroll the crescent dough onto a clean surface and separate into 8 triangles along the perforations.
If desired, brush a small amount of mustard onto the wide end of each triangle. Add 1 slice of ham and ½ to 1 slice of cheese down the center of each piece.
Starting at the wide end, roll the dough tightly towards the point. Tuck the pointed tip underneath to seal. Repeat with remaining dough pieces.
Brush the tops of the rolls with melted butter and sprinkle with seasoning if using. Arrange in the air fryer in a single layer (you may need to cook in batches).
Air fry for 8–10 minutes, or until the croissants are golden brown and the dough is cooked through.
Allow the croissants to cool for 2–3 minutes before serving to avoid burning yourself on the hot cheese.
