Grind or pound all the required ingredients together.
Rub the paste all over the chicken. Ease some of it carefully under the chicken skin, as far as you can go, being careful not to break the skin.
Place the quartered onion, the lemongrass, the lime halves and leaves in the chicken's cavity.
Place the chicken on a roasting dish, cover with foil and leave aside for 30 minutes for the chicken to marinade slightly. Turn the oven on to 190˚C/170˚C Fan.
Put the chicken in the oven and cook for 1 and a half hours, basting after an hour.
Take the foil off for the last 20 minutes to brown the chicken.
Let the chicken rest, covered with foil, followed by a tea towel for another 20 minutes before carving.