Slice up loads of leeks (I put about 3 big ones in the pot and a bit of garlic), put in a large saucepan with butter and fry until soft. Add a stock cube, boiling water and as much chicken as you can get in (I sometimes pull apart a whole, pre-cooked one). Add any seasonings you want and just leave to bubble away on the hob for a good 20 mins. The leeks become soft and delicate and it's like a cross between a stew and a soup. Sounds quite simple and boring but it's incredibly nice.