Transfer the farfalle to a large bowl. Add the chicken, tomatoes, and green onions; toss. Add the vinaigrette and toss again. Taste and adjust the seasoning.
Serve the chicken salad atop the lettuce leaves arranged on individual salad plates.
The vinaigrette will keep in a tightly covered container in the refrigerator for up to 2 days. The completed salad can be made early the day it is to be served; allow it to come to room temperature and assemble the plates with the lettuce leaves just before serving.