Preheat the oven to 180C/350F. Salt and pepper the short ribs. Heat the oil in a large and deep Dutch Oven, then brown the ribs all over on high heat. Remove to a plate.
To the same pot, add the diced onion and cook for 5 minutes over low heat, then add chopped rosemary and sliced garlic, cook for 30 seconds, add the wine, tomato passata (crushed tomatoes) and bay leaves. Return the short ribs back to the Dutch oven, the will be partially submerged in the liquid, cover and cook for 2.5 hours or until very tender and easily come off the bones.
Alternatively, you can cook these short ribs in slow cooker for 8 hours on LOW. Follow the recipe as written until the last part of putting the meat in the oven.