Pre-heat the oven to 190.C. Lightly oil a Magic Roaster tray. Heat 1-2 tbsp oil in a large frying pan, add the onions and sauté for 5-10 minutes until soft.
Pick the sage of the springs, shred it and add to the pan along with the parsnips, season well with salt and pepper. Place the lid on the pan and cook for 10 minutes or so, until the parsnips are soft.
Tear the bread into a food processor and blitz into breadcrumbs. Add to the bowl, along with cooked chestnuts. Crack in the egg, and using your hands mix it all together until well combined.
Using your hands, roll the stuffing into small balls, cover with aluminium foil and bake for 40 minutes. Remove the foil, bake for further 10-15 minutes, then serve.