Sprinkle the osso bucco with salt and pepper and dredge in the flour.
In a casserole dish large enough to hold the pieces in one layer, heat the butter and the oil. Add the garlic clove and toss until brown.
Add the veal pieces and brown them on both sides (or alternately you can heat and braise the pieces in a fry pan and then transfer them to a baking dish). Add the onion, carrots and celery.
Pour the wine over the veal. Squish the tomatoes through your fingers and add them to the dish. Pour the juice from the tomatoes over the top; making sure everything is covered with liquid.
Cover the casserole or if you are using a baking dish, cover tightly with a piece of aluminum foil. Let the veal bake for about 1 ½ hours, checking occasionally to making sure that the liquid is not boiled away.
If you need to add liquid, add either tomato juice or water.
The veal is done when it almost falls off the bone. Serve immediately.