In a Dutch oven, heat the olive oil over low heat. Add the garlic, onions, bay leaves, and rosemary and sauté until the onions are translucent, about 6 minutes. Stir in the cabbage. Sauté until it softens, about 10 minutes. Stir in the tomatoes and sauté for an additional minute. Add the water and salt. Bring to a boil, then reduce the heat and simmer gently until all the flavors marry and the soup is fragrant, about 30 minutes. Stir in the soaked farro, if using, and cook the soup until the grains are tender but still somewhat chewy, about 15 minutes. If using ground farro, stir it into the soup during the last 10 minutes of cooking. Remove the bay leaves and rosemary, taste for salt, and add pepper. Ladle the soup into individual serving bowls. Cover the surface of each with a layer of pecorino shavings. Serve immediately.