Preheat oven to 160°C (140° fan-forced). Lightly spray a large casserole dish with oil. Heat over medium-high heat and sear lamb for 2 to 3 minutes each side, in batches or until browned. Set aside.
Add onion and carrots, cook for 3 to 4 minutes then garlic for 1 minute.
Return lamb to dish with herbs, stock and passata. Season, stir and bring to the boil. Cover and cook in oven for 1 1/2 to 1 ¾ hours or until meat is tender, skimming fat off occasionally. Stir cannellini beans through for last 10 minutes of cooking time, uncovered.
Meanwhile, heat oil in a large non-stick frying pan over medium-high heat. Add breadcrumbs and cook for 2 to 3 minutes or until golden. Add remaining garlic, chilli and lemon zest and cook for 1 to 2 minutes. Drain on paper towel, transfer to a bowl, add parsley, season and stir to combine.
Serve stew sprinkled with pangrattato (crumb mixture) on top of polenta with broccoli.