How to Make It
Preheat the oven to 350°. Heat the olive oil in a large saucepan. Add the minced garlic, onion and carrot and cook over moderately high heat, stirring occasionally, until lightly browned, about 5 minutes. Add the haricot blancs, thyme sprigs, 1 quart of the stock and the water and bring to a boil. Add the bacon and simmer over low heat, stirring occasionally, until the beans are very tender, about 2 1/2 hours. Season with salt and pepper and stir in the parsley.
Meanwhile, rub the lamb all over with the chopped thyme, season with salt and roll into the shape of a roast; tie at 1-inch intervals with kitchen string.
Set the roast in a shallow 12-inch baking dish. Add the remaining 1 cup of stock and roast the lamb for 30 minutes. Add the remaining 6 garlic cloves, cover with foil and roast for 2 1/2 hours, turning once, until the lamb is tender. Transfer the lamb to a carving board. Cover loosely with foil for 10 minutes.
Mash the garlic into the pan juices and season with salt. Carve the lamb into thick slices. Serve the lamb with the pan sauce and the beans.