In a small bowl, mix together yogurt, tahini, lemon juice and spices until smooth. Add water 1 tablespoon at a time until the mixture is pourable.
Add chickpeas to a mixing bowl, along with 1 tablespoon of the dressing, and mash them with a fork until most of the chickpeas are crushed. Stir in the remaining dressing, parsley and scallions until combined.
Divide chickpea salad evenly between lettuce leaves and drizzle with a bit of tahini (if desired).*
* if not eating the wraps right away, store the salad and lettuce separately