Preheat oven to 220 degrees C. Line a baking tray with aluminium foil. Oil lightly.
Combine the breadcrumbs and milk in a small bowl. Soak bread crumbs until milk is absorbed, about 30 minutes.
Combine the breadcrumb mixture, lamb, egg, garlic, olive oil, tomato paste, rosemary, cumin, salt, oregano, black pepper, cinnamon and cayenne pepper in a large bowl. Form lamb mixture into 5cm meatballs and place on the prepared tray.
Cook the meatballs in the oven for 15 minutes or until they are slightly browned. Remove from the oven and set aside.
Combine the meatballs, tomato sauce, chicken stock, fresh mint and chilli flakes in a large saucepan over medium heat. Bring to the boil. Simmer, covered, for 40-45 minutes or until meatballs are cooked through and the sauce is thick.