Mix together the soy sauce, sugar, spring onions, vinegar, maple syrup, chilli paste, sesame oil, ginger, sesame seeds, garlic and seasoning in a medium bowl, until the sugar has dissolved. Transfer 240ml of the marinade to a container, cover and chill. Add the chicken to the bowl with the remaining marinade and toss to coat. Cover and chill for at least 4 hrs or overnight.

Before grilling, let the chicken come to room temperature, about 30 mins. Meanwhile, put the reserved 240ml marinade in a pan and simmer for 8-10 mins or until it has thickened to a glaze-like consistency. Set aside.

Heat the grill to medium-high. Lightly brush the grates with vegetable oil. Shake any excess marinade off the chicken and arrange on the grill without crowding. Grill for 15 mins, flipping the thighs halfway through, until cooked through. Keep an eye on the temperature; if the grill is too hot, the outside of the thighs will burn before the inside is done. Transfer the chicken to a platter and brush very lightly with the glaze. The glaze can also be served on the side as a dipping sauce, along with the doenjang mayonnaise. Serve with corn on the cob and mashed roast sweet potato.