Chicken poached in broth is one of the purest dishes in the canon of cooking. Poached chicken is the Poule au Pot of Henri of Navarre as well as the heart of a New England Boiled Dinner. Here the dish is given an Italian flavour by the addition of parsley-stuffed ravioli.
Chicken cooked in barely simmering water will emerge plump, moist and tender and makes a great base for a wide range of dishes like Capon Salad. In times past, the chicken for the pot would have been a tough old farmyard cock, too full of muscle and sinew to cook in any other way. Consequently it would have taken several hours to produce a texture that was remotely edible. No matter how long you cook one of these birds you never reach that ultimate point of melting tenderness, but you do get an unmatchable flavour in the broth. Such birds are hard to come by, though your butcher will be able to get hold of a boiling fowl - an elderly chicken that has been laying eggs all its life - but my experience of such hens is that they need to be cooked for several hours, only to fall apart at the critical moment when they are becoming tender.
You are unlikely to find a true capon, which is a hand-castrated cock (sorry), but capon-style birds weighing about 3.5kg / 8lb are available. The genuine article has rather dense flesh and is ridiculously expensive. There are such things as Chapon de Bresse, but these are costly oddities that have no place in the domestic kitchen. The assumption here is that you will be working with good-quality, free-range chickens which take much less time to cook but will still give a brilliant result If you use one of the larger capon-style birds, obviously one is the equivalent of two smaller chickens.
You will have lots of chicken left over, which you can use in the Capon Salad or in any recipe calling for cold poached chicken.