1. Melt the butter with the oil in a large flameproof casserole over medium-high heat. In batches, add the lamb and cook, turning occasionally, about 5 minutes, or until browned. Set aside. Cook the onions in the casserole until they begin to soften.

2. Return the lamb to the casserole. Sprinkle with the flour and stir well for 1 minute. Stir in the stock, then add the tomato paste and bouquet garni. Season with salt and pepper. Bring to a boil and cover. Simmer for 1 hour, 15 minutes.

3. Stir in the potatoes, carrots, and turnips and cook, covered, for 15 minutes. Stir in the beans, cover, and cook for another 15 minutes, until the lamb and vegetables are tender.