Brush the inner side of a lamb shoulder with a thin layer of dijon mustard. Lightly season with salt and black pepper. Spread the bread stuffing down the middle of the opened shoulder. Roll the shoulder tightly and tie it up as tightly as you can, using 6 pieces of kitchen string.
Preheat the oven to 240 °C / 465 °F. Place the onions, cut on quarters, large chunks of carrots, halved garlic head in the baking tray. Place the rolled lamb shouled on it. Bake at 220 °C / 430 °F for 20 minutes.
Meanwhile bring the white wine to a boil in a saucepan over a medium high heat. Boil for 2 minutes, so that the alcohol evaporates. Pour the white wine into a baking tray with lamb and bake for another 3 ½ - 4 hours at 150 °C / 300 °F. Cover tightly with thin foil. After 3 hours remove the foil and bake for another ½ hour, or until the meat is nice and soft.
Serve your baked lamb shoulder with bread stuffing and braised carrots.