method
1. Preheat the oven to 350°F (180°C).
2. Season the lamb inside and out. Roll up and tie firmly with string into a neat shape. Peel and thinly slice carrot and onion.
3. Melt the butter in flameproof casserole, add onion and carrot and fry till golden. Add lamb and brown on all sides. Season and add bouquet garni and stock. Cover and cook in centre of oven for 1 hour.
4. Peel turnips and button onions. Place in a saucepan of cold salted water and bring to the boil. Drain and dry on kitchen paper. Arrange turnips and onions around the meat and adjust seasoning. Return to oven and cook for a further 45 minutes.
5. Remove bouquet garni and string. Transfer lamb to warmed serving plate and surround with turnips and onions.
