Bone chicken, or ask your butcher to do this for you. Lay the chicken skin side down on a board.
Heat a medium frypan over a medium heat, add the oil and onion and sauté gently until soft and translucent, about 8 to 10 minutes. Add the garlic and cook until tender, about 2-3 minutes. Add apple cider vinegar and let reduce and caramelise, about 3 minutes. Turn off heat and set aside to cool.
Season the inside of the chicken with sea salt and black pepper.
Layer the tarragon, parsley and sage leaves on the inside of the chicken, then layer over the onion mixture, lemon zest and scatter over chopped bunya nuts.
Roll the chicken around the stuffing, keeping it a tight roll without allowing the stuffing to fall out. Use a skewer to hold the chicken in place if needed, wrap chicken in twine to secure. Wrap in muslin if liked. Store in the refrigerator until ready to cook.
To make the relish, heat oil in a heavy-based saucepan over a low heat and add mustard seeds, cook 1-2 minutes until they start popping. Add the onions and sauté until tender and translucent.
Add cinnamon and cloves, cook until spices are fragrant, about 2 minutes. Add sugar and cook over very low heat until sugar dissolves. Add beetroot and orange rind, then add vinegars. Add water to nearly cover, about 1 cup.
Simmer mixture about 1-2 hours, until reduced and a relish consistency. Bottle in sterilized preserving jars.
To cook chicken, heat stock to a very gentle simmer in a medium-large saucepan. Place chicken in the stock and poach gently until just done, about 40 minutes. Set aside to cool completely and store in refrigerator. When ready to serve, remove muslin and string and slice thickly. Serve with crusty white bread, beetroot relish and Dijon mustard.