Melt some butter in a roasting pan. Brown the duck on all sides along with the onions, bacon, carrots and garlic.
Then roast breast down at 180°C/350°F/gas 4 for 20 minutes. Turn the duck breast up, add the peas, wine, water and sage and season with salt and pepper. Finish cooking until the duck is crisp and the peas tender.
Joint the duck and surround with the peas and juices f