Get out a large, flame-safe cooking pot (with a lid) in which the chicken can fit snugly.
On a washable board, un-truss the chicken, put it breast-side down and press down until you hear the breastbone crack. (As you may imagine, I like this.)* Then press down again, so that the chicken is flattened slightly.
Put the oil in the pan to heat, then brown the chicken for a few minutes breast-side down, and turn up the heat and turn over the chicken, tossing in the feet as you do so. Still over a vigorous heat add the wine or vermouth to the pan and let it bubble down a little before adding the leeks, carrots and celery.
Pour in enough cold water to cover the chicken, though the very top of it may poke out, then pop in the bouquet garni or your herbs of choice, and the parsley stalks (if I have a bunch, I cut the stalks off to use here, but leave them tied in the rubber band) or parsley sprigs.
The chicken should be almost completely submerged by now and if not, do add some more cold water. You want it just about covered.
Bring to a bubble, clamp on the lid, turn the heat to very low and leave to cook for 1½–2 hours.
Serve the chicken and accompanying vegetables with basmati rice, adding a ladleful or two of liquid over each shallow bowl, as you go, and putting fresh dill and mustard on the table for the eaters to add as they wish.
* I didn't write this, Nigella did, but it makes me laugh every time I read it.