Preheat the oven to 180°C. Use string to tie the beef into a neat, compact shape. Heat the oil and butter in a flameproof casserole on top of the stove. Add the meat and cook on medium-high heat, turning it several times, for 6 to 10 minutes, or until it is well browned. Remove the meat, add the onion and carrot, cover and cook on low heat for 5 minutes.
Add the tomatoes, beef stock, bay leaves, salt, cumin and pepper. Return the meat to the casserole, cover and cook in the oven, basting occasionally with the liquid, for 2 1/2 to 3 hours, or until tender. Transfer the meat to a platter; cover with foil and keep warm. Discard the bay leaves and skim the fat from the liquid.
In a small bowl, stir the sour cream and flour together; stir into the liquid in the casserole. Cook over medium heat, stirring constantly, for 3 minutes, or until thickened (do not boil). Serve the sauce with the sliced meat over hot cooked noodles.
Daube de Boeuf à la Provençale: Substitute 2 tablespoons olive oil for the vegetable oil and butter. Cook an extra sliced onion, 3 peeled and chopped cloves of garlic and 125 g diced bacon in the oil. Remove these before browning the meat, then return them to the pan and proceed with the pot roast recipe, using half red wine and half beef stock for the liquid and replacing the cumin with a bouquet garni that includes a strip of orange rind. Omit the sour cream and flour finish to the sauce.