Whisk together the Vinaigrette ingredients in a large bowl. Add the Southwestern Chicken ingredients, except for the lettuce, and stir to combine. Taste and adjust the seasoning.
To serve, divide the chicken mixture between 4 bowls. Place each bowl on a dinner plate with 3 lettuce leaves on the side.
Instruct your guests to spoon the chicken into the lettuce leaves. Fold the sides over the filling and roll to eat.
Remove the core of iceberg lettuce by slamming the root end down on the countertop. Turn the head over, and the core can easily be pulled away from the leaves.