On the day before cooking, spatchcock the chicken by placing it on a chopping board, breast-side down. Score along each side of the spine with a sharp knife or a pair of poultry shears (there should be little to no resistance), remove and reserve the bone for making stock. Flip the bird back over so it’s breast-side up and press down until the breast bone cracks and the chicken can be flattened.
Move to a roasting tray large enough for the spatchcocked chicken and sprinkle with baking powder, lemon zest, and a good covering of black pepper. Place the herbs on the chicken’s surface and completely cover the chicken with salt. Refrigerate for at least 12 hours and up to 24.
Once the chicken has cured, pre-heat the oven to 220C/Gas 7.
Rinse the dry cure from the chicken, pat dry with kitchen paper, and move the chicken, skin-side up, to a baking tray. (If you have a baking tray with a rack, that would be ideal, but it’s not absolutely necessary).
Drizzle a little oil over the skin, and place one or two knobs of butter, to taste.
Roast in the oven for around 45 minutes, basting once or twice, until the skin is crispy and the thigh meat, at the thickest part, registers at 165F. Alternatively, if you don’t have a meat thermometer, check that the juices run clear.