Pour a glug of oil into a heavy bottomed pan or casserole dish. Once it is hot add half the butter. Once that has melted add the lardons and fry until they are very nicely browned, then remove them from the pan with a slotted spoon.
Season the chicken with salt and pepper and brown them in the oil, butter and left over fat from the lardons, then remove them from the pan too.
This is the fun bit – add a heaped teaspoon of mustard seeds to the fat and put on the lid. A glass lid is the most fun, as after a couple of minutes you can watch the seeds burst and fly about all over the place. The make shift tin foil lid is fun too though, as the exploding seeds cause brilliant indentations on the underside.
Once the seeds have all popped (after a minute or so) add the onions, garlic and celery, and gently cook them off until the onions are translucent.
Add a tablespoon of flour to the pan and stir until it has been absorbed – a kind of makeshift roux.
Pour in a little of the cider and stir, and keep adding more, stirring each time, until the cider has absorbed the roux.
Now add the carrots, return the chicken and lardons to the pan and add the sprigs of thyme and the bay leaves. You need to make sure the chicken is completely covered by the cider. Bring to the boil, then reduce the heat and leave to simmer, and cover it almost entirely with the lid – almost, but not quite – you want it to reduce, but not very quickly.
Leave to gently simmer away for an hour, checking occasionally – if it looks like it’s drying out too much add more cider.
When the hour is nearly up slice the chestnut mushrooms and fry them off in the remains of the butter – you want to get them nicely browned – once they are done, add them to the pan and leave it for a further 10 minutes. Serve with boiled potatoes to soak up that delicious sauce.