Start by spatchcocking your chicken. Place the chicken, breast side down, onto a chopping board. Then, with a pair of kitchen scissors cut down either side of the backbone, removing it completely. Turn the chicken over, breast side up, then press down into the middle, with the palm of your hand, until you feel it flatten out like an open book. Cut 2 to 3 slashes into the thighs, to reveal the meat; this will help the chicken cook quickly and evenly.
To make the marinade, melt the butter in a small pan or microwave. Peel and roughly chop the garlic and ginger and place in a blender. Add the turmeric and cinnamon, and finely grate in the lemon zest. Squeeze in the juice from half the lemon, discarding any pips. Pick the coriander leaves and keep to one side, then roughly chop the stalks and add these to the blender too.
Add a good pinch of salt and pepper and pour in the butter and a tablespoon of olive oil. Blitz until you have a vibrant paste, if it is a little thick, add a glug more oil.
Spoon the marinade over the chicken and rub it in all over, working it into all the nooks and crannies. If you are marinating in advance, cover the chicken and pop it in the fridge until needed.
When you’re ready to cook the chicken, preheat your oven to 190ºC/375ºF/gas 5. Place the chicken in a snug-fitting roasting tray and spoon over any marinade that may have fallen off.
Cover the tray tightly with foil and pop in the oven for 1 hour. The chicken should be cooked through but not golden or crispy.
While it is cooking, trim the spring onions and finely slice. Halve, deseed and finely slice the chilli, and roughly chop the coriander leaves. Toss them all together in a bowl and squeeze over the remaining lemon juice. Keep to one side.
Now is the time to stoke your barbecue, or when the chicken is almost ready, place a griddle pan on a high heat and get it nice and hot.
Remove the chicken from the tray and place it skin-side down on the barbecue or griddle. Baste it with any juice from the tray and drizzle it all over with the honey. Griddle it until you have crispy, golden skin.
Serve the chicken scattered with the green garnish, and a side of dressed garden leaves.
NB: Depending on the style of your barbecue, if you have one with a lid, feel free to cook the chicken entirely on there, just be careful and make sure it really is cooked through before serving.