Fill a large saucepan with about 5 litres of cold water and bring to the boil. Clean the bone and add to the water. Trim the meat of any sinews and skin, leaving the layer of fat. Add the topside to the simmering water together with the bay leaves, pepper and juniper berries. Simmer for a further 2-2½ hours. Skim the foam and fat from the top regularly as it cooks. Halve the onion, leaving the skin on, and fry in a dry frying pan (with no oil) until the cut surface is golden brown. Cut the other vegetables into large pieces and add them and the onion to the meat. Cook over a low heat for another hour, until the meat is tender. Remove the meat and strain the broth. Make sure you do not add any salt to the broth while the meat is in it as this will brown and toughen it. Slice the meat and place on a warmed platter. Pour over a little of the broth, season with salt to taste and garnish with chives. Serve with crisply fried potatoes, chive sauce, and apple and horseradish sauce.