Preheat the oven to 200C/400F/Gas 6. Sit the chicken in a large roasting tin and season well with salt and pepper and a drizzle of oil. Place in the oven and cook for about an hour.
For the peri peri sauce, peel and roughly chop the garlic, halve, deseed and finely chop the chillies and place both in a small bowl. Add the rest of the peri peri sauce ingredients and stir to combine.
Remove the chicken from the oven and tip three-quarters of the peri peri sauce over the chicken and spread it all over with the back of a spoon. Peel and quarter the onions, leaving the roots intact, and toss them in around the chicken along with the potatoes. Season them with salt and pepper and then return to the oven to cook for the final 40-50 minutes. At the end of the cooking time the chicken will most likely look burnt, but worry not, this is the peri peri style.
To check the chicken is cooked, pierce the thickest part of a thigh with the point of a sharp knife and the juices should run clear (without any pinkness). Once cooked, carefully lift the chicken from the roasting tin onto a plate and cover it loosely with foil so it can rest and become juicier. Using a slotted spoon remove the vegetables from the tin also, transferring them to a medium ovenproof dish. Then, put them back in the oven (with the oven now turned off) to keep warm.
Carefully pour the oil out from the roasting tin, leaving the juice and sticky bits behind. Put it on a medium heat and add the remaining sauce and the water, stock or red wine. Allow to simmer for a few minutes, scraping up all the sticky bits from the bottom.
Meanwhile, prepare the salad. Squeeze the lime juice into a mug or small bowl and add the sugar (or honey), extra virgin olive oil and a little salt and pepper. Give it a good whisk up. Tip the salad leaves into a large salad serving bowl, pour the dressing over and toss the leaves about.
Returning to the chicken, pour any juices on the plate into the sauce before carving the meat. Arrange on serving plates with the roasted onions and potatoes. Serve with the dressed salad and the sauce in a small jug.
A 1.5-1.8Kg (3Lb 6oz – 4Lb) chicken would be about enough to serve four people but I have given the recipe using a bigger bird so that it gives some leftover chicken for sandwiches the next day. If you use a different size to the one below then work out the cooking time based on 20 minutes per 450g (1Lb) plus 20 minutes. Regardless what size bird you use, cover it after 1 hour and add the onions and potatoes about 45 minutes before the end of cooking time. To speed up the process, use some good sharp scissors to snip the chicken along the backbone to splay it out and cook flat.