1.Combine sauce, honey, mirin, wasabi and oil in medium bowl; reserve ½ cup of marinade in small jug.
2.Place tuna in bowl with remaining marinade; turn tuna to coat in marinade. Cover; refrigerate 3 hours or overnight.
3.Drain tuna; discard marinade. Cook tuna in heated oiled medium frying pan until browned both sides and cooked as desired (do not overcook as tuna has a tendency to dry out).
4.Cut tuna into 24 similar-sized pieces (approximately 2cm each).
5.Place chinese spoons on serving platter. Place 1 piece of tuna on each spoon; top with 1 teaspoon of the reserved marinade and a little ginger.