Preheat the oven to 350°
In a large heavy flameproof casserole heat the oil over moderately high heat until it is hot but not smoking and in it brown the beef, patted dry and seasoned with salt and pepper on all sides. Transfer the beef to a plate, add the onions and the garlic to the casserole, and cook the mixture over moderate heat, stirring, until the onions are soft and golden.
Stir in the tomatoes, the vinegar, the sugar, the bay leaf, and 2 ½ cups water, bring the mixture to a boil, and add the beef. Braise the beef, covered, in the oven for 1 hour, add the carrots, and braise the mixture covered for 1 hour, or until the beef and the vegetables are tender.
Transfer the beef with slotted spoons to a cutting board and let it stand, covered with aluminum foil, for 10 minutes. Skim the fat from the top of the cooking mixture to a boil. Stir the cornstarch mixture and add enough of it to the boiling cooking mixture, stirring to thicken the gravy to the desired consistency.
Simmer the gravy mixture, stirring occasionally for 2 minutes, season it with salt and pepper, and discard the bay leaf.
Slice the beef, arrange it on a heated platter, and transfer the vegetables with a slotted spoon to the platter. Spoon some of the gravy over the beef and serve the remaining gravy on the side. Garnish with the parsley.