Prep the lettuce and toppings. Rinse and pat the lettuce leaves dry so they stay crisp.
Slice green onions and prep any optional veggies now. Keep everything chilled until serving.
Mix the sauce base. In a small bowl, stir together soy sauce, mirin or rice vinegar, brown sugar or honey, sesame oil, and water or broth. Taste and adjust sweetness or salt.
Set aside.
Make the cornstarch slurry. In another small cup, mix cornstarch with water until smooth. This will thicken the sauce later without lumps.
Cook the chicken. Heat a large skillet over medium-high. Add oil, then the diced chicken in a single layer.
Sprinkle with a pinch of salt. Cook, stirring occasionally, until lightly browned and just cooked through, about 5–7 minutes.
Add aromatics. Stir in the garlic and ginger. Cook 30–60 seconds until fragrant, being careful not to burn them.
Simmer with sauce. Pour in the sauce base.
Bring it to a gentle simmer and let it bubble for 1–2 minutes.
Thicken the glaze. Stir the cornstarch slurry, then drizzle it into the pan while stirring. The sauce will turn glossy and cling to the chicken in about 30–60 seconds. If it’s too thick, add a splash of water.
If too thin, simmer another minute.
Finish and taste. Turn off the heat. Add half the green onions and a sprinkle of sesame seeds. Taste and adjust with more soy sauce, sugar/honey, or vinegar as needed.
Assemble the wraps. Spoon warm teriyaki chicken into lettuce leaves.
Top with remaining green onions, sesame seeds, and any crunchy add-ons. Serve immediately.