Preheat oven to 180°c

Using a wooden spoon, beat the Vegemite, butter and ¼ cup parsley in a bowl until combined. Alternatively, process in a small food processor.

Rinse the chicken inside and out and pat dry with paper towel. Gently loosen the skin from the breast meat with your hands, pushing as far as possible without tearing the skin. Spread the butter mixture all over the breast meat, then pat down the skin to cover.

Spread the onion over the base of a roasting pan, then place the chicken, breast-side up, on top. Rub 1 tbsp macadamia oil over the chicken and season. Place the reserved lemon inside the cavity, then truss the legs with kitchen string.

Roast for 1 hour 10 minutes or until the juices run clear when the thickest pat of the thigh is pierced. Set chicken aside to rest, loosely covered with foil, for 10 minutes.

Bring the stock to the boil in a saucepan over medium-high heat, then pour over the couscous in a bowl. cover with a clean tea towel and set aside for 10 minutes. Add 1 tbsp macadamia oil, season, then fluff with a fork. Add the macadamias, lemon zest, broccolini, roasted onion and remaining ¼ cup chopped parsley and stir to combine.

Using poultry scissors, cut chicken into quarters and serve with couscous, drizzled with pan juices.