Greek Salad Sandwich

In a food processor, pulse chickpeas, 1 tablespoon lemon juice, 1 tablespoon olive oil, and parsley until finely chopped. In a small bowl, stir together onion, 1 tablespoon lemon juice, and 2 teaspoons olive oil and season with salt and pepper. In another small bowl, mash feta with 1 tablespoon olive oil. Spread chickpea mixture on 4 slices bread. Top with cucumber, tomato, and onion mixture; season with salt and pepper. Spread feta mixture on 4 more bread slices and place on top of sandwiches.