In a large deep pan, add some oil on medium heat and cook the onions until softened, then add the sliced peppers and on a lower heat, let slowly cook while you make the meatballs.
In a large bowl, add the lamb mince, egg, garlic, chopped parsley, salt and pepper for seasoning, and oregano.Using your hands, gently combine then make meatballs approx the size of a golf ball.
In the pan, move the onion and peppers to the side and add the meatballs, turning until they are browned all over (you may need to batch cook them if your pan isn't large enough).Once done, add all the cooked meatballs back into the pan and add the passata, harissa, stock, orzo and bring to a gentle simmer. Pop the lid on and leave for approx. 10 mins
Remove the lid and add torn pieces of mozzarella and chopped parsley. Serve.