Cut the chicken breast into even 1" (2.5cm) cubes.
Add all the marinade ingredients to a large bowl and stir to combine. Add the chicken and toss until evenly coated. Marinate for 10 minutes.
Meanwhile, add all the peanut sauce ingredients, except the chopped peanuts, to a small saucepan. Cook over low heat for 3-5 minutes, stirring until smooth and slightly thickened. Remove from the heat. Stir in the chopped peanuts if using smooth peanut butter.
Towards the end of the marinating time, preheat the air fryer to 190°C/375°F for 5 minutes.
Thread the chicken onto skewers, leaving a little space between each piece. Metal, bamboo or wooden skewers can be used. If using metal skewers, turn them carefully, as they will be hot.
Arrange the skewers in a single layer in the air fryer basket. Cook at 190°C/375°F for 7 minutes, then turn and cook for another 7 minutes.
Increase the temperature to 200°C/400°F and cook for a final 2 minutes, or until lightly charred around the edges and the chicken reaches an internal temperature of 75°C/167°F.
Brush the hot skewers with the peanut sauce, then garnish with chopped spring onion, fresh coriander and extra chopped roasted salted peanuts.
Serve immediately with the remaining peanut sauce. To make it a complete meal, serve with quinoa or rice and a fresh salad.