Pot roast a chicken with a lemon and an onion in the cavity, with about half a cup of chicken stock in the pot. Take the lid off for the last half hour to brown.
Take your chicken out of the pot to rest, and put the lemony stock into a saucepan. Put in a good dollop of sour cream (creme freche in England)and several good handfuls of raw watercress. Take a mouli and whizz the sauce briefly so you still have leafy flecks, then warm through again without boiling. Season as necessary. Slice your chicken and put it onto plates. Spoon the watercress sauce over your chicken and serve with boiled new potatoes or mash. I also like leeks with it.
Singing "The Watercress Girl" during preparation is optional.