Arrange the leeks and apple wedges in
a single layer in a wide, shallow casserole
dish with a lid. Poke the sprigs of thyme
in among the leeks and pour over the
stock. Season and dot the butter on top.
Place over a medium heat, bring to
the boil, then put the lid on and gently
simmer for 15 mins or until the apples
and leeks are tender.