use small red or white potatoes. My note: I also insert slices of garlic (medium cloves, quartered) into slits made in the roast at about 8 cm intervals with a sharp knife. This adds a wonderful subtle flavor to the meat. Mince the garlic clove and mash to a paste with quarter tsp salt. Blanch onions in boiling water 2 minutes, drain, and peel. Cut carrots into 1 cm pieces. Cook potatoes in boiling salted water for 10 minutes, drain, and halve. In a small bowl whisk together the mustard, the garlic paste, the chopped rosemary, the chopped thyme, the soy sauce, the white wine, and salt & pepper to taste, add 2 Tablespoon of the oil in a stream, whisking, and whisk the mixture until it is combined well. Brush the lamb generously on all sides with some of the mustard mixture, and let it marinate in a lightly oiled roasting pan, covered and chilled, for at least 6 hours or overnight. Let the lamb come to room temperature and brush it with the reserved mustard mixture. In a bowl toss the onions with 1 Tablespoon of the remaining oil, add the onions and carrots to the pan, and roast them with the lamb in the middle of a preheated 230ºC . oven for 15 minutes. In the bowl toss the potatoes with the remaining 1 Tablespoon oil and add them to the pan. Reduce the heat to 180ºC . and roast the lamb and vegetables, stirring the vegetables occasionally, for 1 hour and 15 minutes, or until a meat thermometer registers 60ºC . for medium-rare meat. Transfer the lamb to a large platter and let it stand for 20 minutes. Transfer the onions and the potatoes with a slotted spoon to a serving dish, leaving the carrots in the pan, and keep them warm, covered. Make the gravy: Pour off the fat from the pan, add the wine, and deglaze the pan over moderately high heat, scraping up the brown bits. Boil the mixture until it is reduced by half and strain it through a sieve into a saucepan, pressing hard on the carrots. My note: I stopped at this point, adding juices from the lamb platter, and used the resulting sauce for the meat--it was delicious! Add the broth and bring the mixture to a boil. In a small bowl knead together the butter and the flour until the mixture is combined well and add the mixture to the gravy a little at a time, whisking. Add any juices that have accumulated on the platter and salt and pepper to taste and simmer the gravy, whisking occasionally, for 3 minutes, or until it is thickened. Spoon some of the potatoes and onions around the lamb, and garnish the lamb with fresh thyme and rosemary sprigs. Serve the lamb, carved, with the gravy.