Preheat the oven to 350 degrees. In a casserole large enough to hold the meat, heat the butter. When foaming subsides add the onions and carrots and saute for about 10 minutes or until they take on some color. With a slotted spoon remove them and reserve for later.
Add the oil to the casserole and heat over high heat. Add the beef and brown the meat on all sides; this should take 15 minutes to get a deep golden color. Return the vegetables to the casserole, stuffing them underneath the meat. Add the garlic, tomatoes, bouquet garni. Heat the casserole until you hear it sizzle, drape the meat loosely with aluminum foil, cover the casserole tightly and place it in the lower third of the oven.
Cook for 1 hour, turn the meat over, lower the heat to 325 and continue to cook until the beef is tender, another 1 1/2 to 2 hours. Remove the meat to a platter. Strain cooking juices into a saucepan, pressing down hard on the vegetables to extract their liquid. Let liquid settle for a minute, then skim off surface fat. Heat the liquid and reduce slightly; adjust seasoning. Slice the roast and spoon the gravy over the top. Serve with braised carrots and boiled parslied potatoes (make extra for cold potato salad and beef salad next day).