Add onions, carrots and celery to the pot, and lightly brown. Add garlic and tomato paste, and cook for 2 minutes. Add 1 cup of stock, and stir bottom of pot to loosen bits. Return shanks to the pot, add wine, rosemary, thyme and bay leaves. Liquid should always cover the shanks about halfway. Add stock to correct level, and reserve any extra to add later, if needed. Cover and place in the preheated oven for 2½ hours. Check after about 1½ hours, and see if any additional liquid is needed. Add more stock and/or wine if necessary.