Preheat the oven to 190°C.
Rub the gammon joint with a little of the groundnut oil. Smear the crushed garlic on top, then season with salt, pepper, chopped rosemary and the sage leaves.
Place in a roasting tray and scatter the parsnip and bay leaves around the joint.
Drizzle the rest of the groundnut oil on the parsnips and season them. Cover the tray loosely with aluminium foil.
Roast for 80 minutes then remove the tray from the oven and discard the aluminium foil.
Return to the oven for a further 10 minutes.
Remove after 10 minutes and allow to rest covered loosely with aluminium foil for 5-10 minutes. Arrange everything from the tray on a serving plate when you are ready to serve.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.