Step 1

Put all the dry-brine ingredients into a mortar and grind to a fine powder with a pestle, then add to a large bowl. Add the chicken and rub the brine in really well, ensuring it is well covered inside and out. Put a cooling rack over a tray and sit the chicken on top. Chill uncovered in the fridge for at least 4 hours and preferably overnight, but no longer than 24 hours.

Step 2

Heat the oven to 220C/fan 200C/gas Pat the chicken all over with kitchen paper, removing as much moisture as possible.

Step 3

Put the butter, tarragon and garlic into a bowl with some seasoning and mix well. Carefully pry the skin on the chicken breasts and legs away from the meat with your hand, being careful not to tear the skin. Spread the butter underneath the skin, pushing right down and around the legs.

Step 4

Put the onion, carrot and celery into the bottom of the roasting tray and put the chicken on top. Cook for 15 minutes then reduce the oven temperature to 180C/ fan 160C/gas 4 and cook for 1 hour, basting the bird with the butter every so often.

Step 5

Put the chicken onto a plate and, with several pieces of tin foil, cover the legs tightly, but don’t cover the breasts. Leave for 20 minutes to rest, then carve. Squeeze the lemon into the roasting tin and serve these buttery veg and juices alongside the chicken