Pour off the fat. Add the remaining 1 tablespoon of oil and the carrots to the casserole and cook over moderate heat for 3 minutes. Add the celery, leek and garlic and cook until starting to soften, 2 minutes. Add a large pinch each of salt and pepper and the barley. Cook over moderately high heat, stirring, until the barley starts to toast, 1 minute. Add the stock and water and bring to a boil. Cover and simmer over low heat, stirring occasionally, until the barley is almost tender, about 20 minutes.