Before you start, preheat oven to 220°C (or 200°C fan bake).
Melt first measure of butter and prep onion. Combine both in a medium bowl with stuffing mix ingredients, egg, milk and salt until well combined. Set aside.
Pat chicken dry, place on a large, lined roasting tray, drizzle with oil and season with salt and pepper. Prep parsnip, Brussels sprouts and carrots and place around chicken, on tray. Season with salt.
Roll stuffing mix into golf-ball sized balls and place on top of veggies in tray. Place tray in oven and cook for 50-60 minutes, until chicken is cooked through and veggies are tender. Test chicken is cooked by piercing a knife into the thickest part of the thigh, the juices should run clear. Set aside to rest.
While chicken rests, make gravy. Melt second measure of butter in a medium pot on medium heat. Add gravy spice blend and cook for about 30 seconds, until fragrant. Slowly add water while whisking and simmer for about 2 minutes, until thickened.
To serve, carve chicken and serve with veggies, stuffing and gravy.