How to Make It
Coarsely mash chickpeas in a large bowl with a fork. Stir in celery, parsley, mayonnaise, shallot, lemon juice, Dijon, salt, and several grinds black pepper.
Spread 1 side of toasted bread slices with desired amount of mayonnaise and Dijon. Place 1 lettuce leaf on each of 2 bread slices. Top with chickpea salad, and cover with remaining bread slices.