Split your rolls or bread in half and drizzle both sides generously with olive oil. Spoon the smashed chickpeas on the bottom half first, then the onion, and a little drizzle of vinegar. Add eggs, if using, and season this layer with salt and pepper. Add the capers, olives, and cucumber. Add another gentle drizzle of olive oil and smaller dribble of vinegar, if you wish. Finish with the tomatoes and more salt and pepper on top, then basil, if you’re using it.