1. Warm oil in a large skillet over medium-high heat. Add onion and sauté until softened, about 3 minutes. Add garlic; sauté 1 minute longer. Stir in turkey and cook, stirring, until almost cooked through, about 5 minutes. Add broth and hoisin sauce. Cook, stirring and breaking up clumps of turkey, until turkey is cooked through, 5 to 7 minutes. Remove from heat and stir in teriyaki sauce, bean sprouts and carrots. (You should have about 6 cups of filling.)
2. Spoon about 1/4 cup of filling into center of each lettuce leaf. Serve with soy sauce, if desired.