Step 1

Preheat the oven to 180C.

Step 2

To make the herb butter, whiz all the ingredients in a blender or food processor until finely chopped and combined. Season well.

Step 3

Pat chicken dry inside and out with paper towel. Gently work your hands between the skin and the flesh of the breasts to loosen the skin, being careful not to make any holes, then spread half the butter over the flesh. Spread the remaining butter all over the chicken skin. Place lemon halves and tied herb sprigs in the cavity. Scatter onion in a roasting pan and place chicken on top.

Step 4

Place the quartered lemons around the chicken, then roast, basting frequently, for 11/4 hours or until the juices run clear when the thickest part of the thigh is pierced. Transfer the chicken to a serving platter, loosely cover with foil and set aside to rest.

Step 5

Discard the onion and lemon in the roasting pan, then skim off any oil from the pan juices. Place pan on the stovetop, add the stock, then stir with a wooden spoon over medium-high heat, scraping the base of the pan to deglaze. Combine the cornflour with 1 tbs water to form a smooth paste, then add to the pan and stir to combine. Bring to the boil, then reduce heat and simmer for 4-5 minutes until thickened. Strain the sauce into a jug and serve with the roast chicken and herbed couscous salad.