Preheat the oven to 180°C, fan 160°C, gas 4. Place the lamb in a large roasting tin. Pierce the lamb flesh about 8 times with the tip of a sharp knife and insert a slice of garlic and small sprig of rosemary into each hole. Cover loosely with foil and roast the lamb in the oven for 1 hour 30 minutes.
Make up the Paxo stuffing following the pack instructions, adding the chopped apricots, if you want a sweet twist. Divide and shape into about 18 stuffing balls. Place in a baking tray and set aside.
Increase the oven temperature to 200°C, fan 180°C, gas 6. Uncover the lamb and add the onion wedges to the roasting tin, turning them to coat in the pan juices. Roast the lamb and onions for a further 30 minutes until the onions are tender and the lamb is cooked to your liking. To check how well done the lamb is, use a meat thermometer inserted into the centre of the joint at the thickest point, for medium it should read 70-75°C and for well done, 75-80°C.
Remove the cooked joint, cover with foil and leave to rest in a warm place for 25-30 minutes before carving. Cook the tray of stuffing balls in the oven for 25-30 minutes until browned and piping hot. Make up the Bisto onion gravy granules following the pack instructions. For a richer flavour, replace 50ml of the boiling water with red wine.
Arrange the lamb on a warmed platter with the onion wedges and stuffing balls and garnish with a few rosemary sprigs. Serve the gravy in a warmed gravy boat on the side.