How to Make It
Mix together mayonnaise, lime juice, wasabi paste, 1 teaspoon mirin, and ￼½ teaspoon salt in a bowl. Stir together sesame seeds and nori in a separate bowl.
Whisk together lemon juice, sesame oil, and remaining 1 tablespoon mirin and ￼¼ teaspoon salt in a large bowl. Add tuna and gently toss to coat.
Pick 18 large leaves from lettuces (reserve remaining interior leaves for another use). Top leaves with cabbage, tuna mixture, and avocado slices.
Drizzle with wasabi-lime mayonnaise and top with sesame seed mixture.