Whisk together the marinade ingredients, put the chicken into a dish, then pour over the marinade, mixing to coat. Cover, then chill for at least 20 mins, or up to a day if you have time.
Heat oven to 180C/fan 160C/gas 4, and lift the chicken out of the marinade into a roasting tin. Roast for 40 mins, pour over the remaining marinade, then cook for a further 30 mins until golden and sticky. Sprinkle with the spring onion, then serve.