Heat the oven to 375°F. Line a rimmed baking sheet with parchment paper.
In a large bowl, combine the ground turkey, egg, panko, ¼ cup scallions, garlic, ginger, soy sauce, 2 tablespoons of the hoisin sauce, and sesame oil. Mix gently until combined, taking care not to pack the mixture too tightly.
Shape the mixture into a compact loaf on the prepared baking sheet. Bake until the center reaches 165°F, about 45 to 55 minutes.
Carefully spread the remaining hoisin sauce over the top of the meatloaf. Return it to the oven for 5 minutes, until the glaze is warm and glossy.
Let the meatloaf rest for 10 minutes, then slice it. Serve the slices in the butter lettuce leaves and top with the reserved scallions and sesame seeds.