Combine cubes of tuna and hamachi. Marinate fish in soy sauce, lemon juice, sesame seeds, ginger, garlic and oil in a small bowl.;
VINAIGRETTE: To prepare mussel liquid, steam mussels in water with sliced ginger.
Puree all ingredients in a blender until emulsified.
LOBSTER OIL: Brown lobsters, carrot, celery and onion in olive oil. Add tarragon, coriander seed and tomato paste. Add grapeseed oil until lobsters are covered. Cook for 1 hour then strain.
To assemble tuna cubes: layer cubes with seaweed and garnish with sliced green onions. Pick skewer through the cubes. Drizzle with sea urchin vinaigrette.