Prepare the chicken: Remove excess fat from the chicken thigh. Place skin-side down and make deep cuts 2cm apart along the length.

Place marinade ingredients and chicken in a freezer bag: Add marinade ingredients to a resealable freezer bag, mix well, then add the chicken. Seal the bag and massage the marinade into the chicken.

Flatten the bag and freeze: Lay the bag flat on a tray, remove air from the bag, seal tightly, and freeze completely.

Defrost the chicken completely. Cut green onions into 4cm lengths and slice shiitake mushrooms thinly. Remove chicken from the bag, drain excess marinade, and coat chicken with flour.

Heat 1 tbsp salad oil in a frying pan over medium heat. Place chicken skin-side down and cook for 2 minutes on each side. Add shiitake mushrooms, cover, and steam on low heat for 8 minutes.