In a medium bowl, use a potato masher or fork to mash the chickpeas to your desired consistency.

Add the celery, cranberries, walnuts, mayonnaise, and lemon juice. Stir to combine.

Sprinkle with feta cheese then stir again, gently, just until incorporated.

To build the sandwiches, layer greens, if using, onto the bottom piece of bread. Spread the chickpea salad to generously cover the greens. Top with the second layer of bread then cut in half and serve.