In a large bowl, combine mayonnaise and lemon juice. Stir until smooth, adding salt and pepper to taste.

Open chickpeas, drain and rinse. Mash half the chickpeas in a bowl for 1-2 minutes until chunky.

Fold mashed chickpeas and remaining whole chickpeas into the dressing. Add shallots, carrot, and green onion. Mix well.

Place lettuce on two slices of bread, top with chickpea salad mixture, and cover with remaining bread.

Press down gently on the sandwiches and slice diagonally before serving.