Start by soaking the bread in milk. When it becomes soft, squeeze it and put it in a bowl. Add the egg, grated Parmesan, salt, pepper, a pinch of nutmeg and parsley. Finally add the guanciale Tagliette cut into three. Mix everything well until you get a homogeneous mixture. If necessary, you can add breadcrumbs.
Cut the mozzarella into cubes of about 1 cm. With slightly damp hands, take a little of the prepared mixture and make a hollow: fill it with a cube of mozzarella. Close with some more mixture and form the meatballs. Roll them in a plate with beaten eggs and then in breadcrumbs to cover them completely.
Fry them, a few at a time, in plenty of hot vegetable oil. Drain them with a slotted spoon, let them dry on kitchen paper and serve the bread balls with guanciale Tagliette and mozzarella, while still hot.