Whisk together the soy sauce, Hoisin, honey, lemon juice, crushed garlic and chilli flakes. Taste and adjust the seasoning by adding more soy, honey or lemon juice.
Place the chicken in a suitable marinating dish and pour over the marinade. Make sure the chicken is completely covered.
Cover with plastic wrap and allow to marinade for at least 30 minutes but up to 24 hours in the fridge.
Transfer the chicken to a sheet pan and spoon over one third of the marinade. Place in the oven and bake for 15-20 minutes until cooked through.
Pour the remaining marinade into a saucepan and reduce until thick and sticky (the consistency of honey is good).
Remove the chicken from the oven and switch on the oven's broiler.
Glaze the chicken then place back in the oven and allow to caramelize for a few minutes. Repeat this a few more times until the chicken is sticky and caramelized.
Remove from the oven and scatter over sesame seeds and spring onion then serve.