Heat 2 tablespoons olive oil in a large ovenproof casserole or frying pan. Add the carrot, celery and capsicum and cook over medium heat for about 5 minutes.
Add the zucchini and mushrooms and cook for another 5–7 minutes, until the vegetables have softened and some of their moisture has evaporated.
Stir through the tomato paste, oregano, basil and smoked paprika and cook for another minute.
Add the crushed tomatoes and chicken stock. Season with salt and pepper. Bring to a gentle simmer and cook uncovered for 15–20 minutes.
Stir through the drained cannellini beans and balsamic vinegar. Simmer for another 5 minutes.
Spoon approximately half the bean and vegetable mixture into a large baking dish. Nestle the browned chicken meatballs into the sauce.
Spoon the remaining sauce and beans around and partially over the meatballs. You still want to see the tops rather than completely submerging them.
Bake uncovered for 20–25 minutes, or until the sauce is bubbling and the chicken meatballs are cooked through.