In a large bowl, mix together beef, cabbage, carrot and onion. Stir in the egg, sugar, salt, soy sauce and vegetable oil.

Place a large teaspoonful of filling in the center of a wonton. Moisten the edges of a wonton with a few drops of water. Then fold the wonton in half and pinch the edges together to seal. Create a ripple pattern along the pinched edge by pinching and gently pushing together small segments of it. Repeat with remaining wontons.

Brush each wonton with melted butter.

Fry in air fryer at 400 for 4 minutes.

Optional: serve with a sweet and sour dipping sauce.