Detach the leaves of the lettuce from their head, discarding any blemished ones. Wash them in cold water, shake thoroughly, and dry in a cloth towel or in a salad spinner. Lay a few leaves one on top of the other and cut into thin longitudinal strips, about ¼inch wide.
If Using Drained Canned Chickpeas
Squeeze off the skin from every pea, put the chickpeas in a saucepan with enough water to cover, and warm them up at a gentle simmer for 2 minutes.
If Using Cooked Dried Chickpeas
Drain them, reserving the water in which you have boiled them. Squeeze off the skin from every pea, put the chickpeas in a saucepan with enough of the reserved water to cover, and warm them up at a gentle simmer for 2 minutes.
Retrieve about ¼cup of the warm chickpeas, using a slotted spoon, and put them in a salad bowl. Mash them to a pulp with the back of a spoon, then trickle in the olive oil, beating it in with a fork. Add the salt, vinegar, and black pepper, continuing to beat with the fork to incorporate the condiments smoothly.
Drain the remaining chickpeas and add them whole to the bowl together with the shredded lettuce. Toss thoroughly and serve at once.