Place the chopped cashews into a dry skillet set over medium heat. Toast for 3 to 4 minutes, swirling constantly until fragrant and lightly golden, then transfer immediately to a small bowl to prevent burning.

In a small skillet, warm 15 ml of the reserved olive oil from the tuna over medium-low heat. Add the minced ginger, garlic, and scallion whites, cooking gently for about 1 minute until fragrant without browning.

In a medium bowl, whisk together the soy sauce, toasted sesame oil, fresh lime juice, and honey. Pour in the warm ginger-garlic mixture and whisk until emulsified.

Flake the drained tuna into the dressing, folding gently to coat the fish while leaving visible chunks. Stir in half of the toasted cashews and the sliced scallion greens.

Arrange 8 to 12 crisp lettuce leaves on a wide platter. Spoon equal portions of the seasoned tuna mixture into each leaf, then garnish with the remaining toasted cashews, chili flakes, and extra scallions.