Using a large knife, roughly chop up the chicken, giving it some texture, then set aside. Roughly break up the bread into a bowl and pour over the milk, tossing it together, and set aside until the milk is absorbed.
Meanwhile, peel the garlic, and pick and finely chop the parsley.
Put the soaked bread, olives, capers, garlic and Parmesan into a blender and blitz until combined. Add the chicken and break in the egg, then pulse very briefly, until the mixture is blended enough to be moulded into balls but is still a little chunky.
Season to taste with sea salt and black pepper, then roll the mixture into small balls, about 2.5cm wide (if the mixture is a little too wet to work with, add some extra breadcrumbs until it comes together).
Place the meatballs in a greased ovenproof dish. Drizzle generously with oil and bake in the oven for 30 minutes, turning the balls halfway so they’re golden on all sides.
While the meatballs are cooking, make your sugo: heat 2 tablespoons of oil in a large frying pan over a medium heat, peel and crush in the garlic and cook for 3 minutes, or until softened but not coloured.
Tip in the tinned tomatoes, then fill the empty tin a third of the way up with water and add this as well. Cook over a high heat for 8 to 10 minutes, stirring occasionally, until the sauce has reduced and thickened. If your tomatoes taste slightly acidic, stir in the sugar to sweeten. Season with salt and pepper.
Add the sauce to the dish 5 to 10 minutes before the meatballs have finished cooking. Serve with the parsley scattered on top.