di pane are an opportunity. Not a solution to reanimate stale bread. The radical change in shape make this a remarkable dish. Sphere shaped food is a league of its own.You can add ingredients to the mixture. Herbs such as parsley or oregano for example. Minced capers do wonderfully well, too.Regarding the cheese, use hard cheese. Caciocavallo or similar. Remember that the cheese contributes much to the final flavour. The polpette di pane can be briefly cooked in tomato
sauce. Use them for starters or your aperitive. Few things are more finger food-able.