[madcat]

Core, dont peel, and chop into roughly 1" pieces 500g/1lb apples.  Any sort of eating or cooking apples - I tend to make the recipe with the apples from the fruit bowl that have seen better days.  Peel and chop an onion roughly and put to melt gently in a little vegetable oil, while you scrub a large-ish spud and chop into roughly 1" cubes.  Dont bother to peel it.  When the onions are soft add the potato and cook for a few minutes.  The starch takes up any excess oil so it thickens and there is no oil left on top of the soup. Stir in the apple. Add 2 pints of vegetable stock (or chicken oxo does at a push) and bring to the boil.  Turn down and simmer until the potato is cooked through.  Its not fussy if you leave it simmering longer than that, until you get to it. 
Cool a bit, liquidise or blend and then pass through a sieve into the serving bowl (ideally one you can microwave).  The sieve gets the potato and the tougher bits of apple skin out so you have a smooth velvety soup.  Add salt, pepper, a little ground nutmeg and reheat.  Float a slice of stilton (or any blue cheese that melts) on to serve and put the stilton on the table so everyone can put their own in the bowl and pour over hot soup.  Some like lots of cheese, others not so much so this way makes it flexible. 
I use the end of the Christmas stilton, or second quality stilton from the market or leftovers or sometimes - shock horror I buy some from Aldi just for this soup!  I have also been know to use cheddar too - it is different but works fine.  I call it ploughman's soup then.   

[Snoop]

Sounds delicious, madcat. Thanks for posting. I love blue cheese in soup.