Stir together 3 tablespoons soy sauce, 3 tablespoons water, vinegar, 1 teaspoon sesame oil, and sliced chiles in a small bowl.
Heat broiler. Mix together 1 1/2 teaspoons soy sauce, the ginger, garlic, and the chopped scallion and chile in a medium bowl. Mix in turkey until just combined.
Form mixture into 24 balls, dipping hands in water if needed to prevent sticking. Brush meatballs with 1 teaspoon sesame oil on a baking sheet. Broil 8 inches from heat source until golden brown and cooked through, 5 to 7 minutes.
Meanwhile, heat remaining teaspoon sesame oil in a large nonstick skillet over medium-high heat. Cook mushrooms until just starting to brown, about 2 minutes. Reduce heat to medium. Cook, covered, until tender, about 3 minutes more. Add remaining 1 1/2 teaspoons soy sauce. Toss to coat.
Arrange lettuce leaves on a platter, and top each with 1 meatball. Top with mushrooms, and sprinkle with sliced scallion. Serve with dipping sauce.
Dipping sauce can be refrigerated for up to 1 day. Shaped meatballs can be refrigerated for up to 1 day.
Made the recipe today and was disappointed. The ingredients sounded very flavorful but found the meatballs and mushrooms quite bland and the dipping sauce too vinegary.
Made this recipe tonight and it did not taste very good. Followed the recipe exactly but the turkey meatballs were very bland and the shiitake mushrooms were awful. My husband and I love asian food but this recipe is not a keeper for us.