Roast sesame seeds in a pan without fat. Remove.
Mix mayonnaise, orange juice, soy sauce, sesame oil and wasabi. Peel ginger, grate finely and stir in.
Wash the tuna, dab dry and cut into very small cubes. Halve, stone and peel the avocados. Dice the flesh just as small. Season both with salt and pepper and carefully fold into the dressing.
Wash the chives and cut into small rolls. Arrange tuna on Asian porcelain spoons or small plates. Sprinkle with chives and sesame seeds.