Heat the olive oil in a large pan over medium-high heat. Add the diced onion and soy sauce, and cook for about 5 minutes, stirring occasionally, until the onions are soft and translucent.
Stir in the minced garlic and cook for an additional minute, just until it becomes fragrant.
Add the ground turkey to the pan. Use a wooden spoon to break it into small pieces as it cooks. Stir frequently until the turkey is no longer pink, about 5 minutes.
While the turkey cooks, prepare the sauce. In a small bowl, whisk together the soy sauce, rice vinegar, brown sugar, sesame oil, red pepper flakes, and ground ginger until well-combined.
Pour the sauce over the cooked turkey mixture. Let it simmer for 2–3 minutes to slightly reduce and intensify the flavors.
Arrange the lettuce leaves on a serving platter. Spoon the turkey mixture into each leaf, garnish with your favorite toppings, and serve immediately!