To prepare the Teriyaki sauce, place a small saucepan onto the BBQ. Pour in the soy sauce, rice wine vinegar and water. Add sugar, ginger and corn flour. Bring to boil over a low heat stirring gently for 5 mins until glossy.
Season the burgers and add into a frying pan cooking for 3 – 4 minutes, turning occasionally. Finish off the burger placing some cheese on it to melt (if you want).
Toast your brioche buns directly onto the grill of the BBQ for 1 min, this will create a barrier for the juicy marinade and stop them from going soggy.
To serve, place the burgers (topped with cheese) into the buns and add another layer of the Teriyaki sauce and sprinkle with the chopped spring onion.