Heat oven to 200C/180C fan/gas 6. Sit your chicken in a roasting tin. Ease the skin away from the breast and push the butter underneath the skin. Tuck a couple of fresh sage leaves in there too, if using.
Sprinkle the skin with the sea salt and some black pepper. Pour water into the bottom of the roasting tin to fill it about 1-2cm deep.
Cover the chicken with foil and roast for 1 hr. Remove the foil and continue to roast for 20-30 mins until the skin is golden, the chicken is cooked and all the juices run clear.
Pour the juices into a jug to use in gravy. Put the chicken on a board and cover with foil and a clean towel or tea towel. Leave it to rest for 15-20 mins, then carve.
Want to try a twist on seasoning?Instead of seasoning your chicken with salt and pepper, try sprinkling the meat with chicken salt. To make chicken salt, put 1 chicken stock cube in a mini food processor along with 100g coarse sea salt and 2 tsp thyme. Pulse a few times to grind the stock cube and to disperse it through the salt.