There is only 1 way to do roast chicken and this recipe never fails. Take one chicken, cut a lemon in half and squeeze it over the chicken, stuff the lemon inside the chicken, sprinkle tarragon over the top, drizzle olive oil over the top, put a tiny bit of water in the bottom of the tray and roast for 1.5 - 2 hours. The secret to roast chicken is to always stuff either an onion or lemon in it as it keeps the chicken moist.
If you're buying it from a decent butcher then that is 90% of the success of a roast chicken solved there. We have roast chickens once a fortnight I'd say, and the few times I have bought from supermarket - even if organic - they are far inferior to the free range butchers one. Too tough, not juicy enough. You can really tell the difference
Once you have your beautiful butcher's chicken, stuff a lemon in the cavity, sprinkle liberally with salt and pepper, smear in butter and roast based on Delia's instructions (I think 190C, 20 mins per lb. She allows up to 20 mins over but I find the chicken rarely needs thsi extra 20 mins). The lemon makes the juices lovely for gravy.
Gravy: put roasting tin directly over the heat, add a good glug of white wine to help lossen the tasty bits off the bottom, scraping them off with a wooden spoon. Mix a good teaspoon of cornflour with a splash of cold water and add to the pan, keep stirring until it thickens. Pour in a ladleful or thereabouts of chicken stock, whisk to mix, add more stock until you've got the consistency you want. By this time more juices should have been released from the chicken - add these to your gravy. I usually then tip all this into a pan to keep warm on hob until I'm ready to serve as gravy should be piping hot.
Cook's treat: always eat the wings as soon as the chicken is out of the oven while you're fiddling with other bits of dinner. Mouth-burningly hot but utterly delicious!
I'd say get close to 2kg. That should be plenty for 5 and may leave pickings. We get a 2kg for 2 adults, 2 small children and always have plenty leftover for another meal or two during the week.
I would get about a pound per person, so round about 2.5 kg bird.
to cook: preheat the oven to as hot it goes. rub the chicken with oil and sprinkle over some stock granules. put in the very hot oven for about 20 min then turn down to about 160 and cook for 20 min per pound. baste occasionally.