Use a pot of creme fraiche, some chopped herbs if liked, pinch of salt/pepper and a good couple of handfuls of grated strong cheddar.
Just bung the lot in a pan and warm through til the cheese is melted. Be careful not to overcook though as the creme fraiche will go all runny and horrid.
Shamelessly stolen from a Jamie Oliver Sainsbury's ad and adapted to suit..... - goes lovely with fish though!
I love my cheese sauce, i have it over my sunday dinners now instead of gravy. I cant get enough of it. I do cream, philly and grated cheese. Last week i done cream with blue cheese and had that over steak.
just made the quickest cheese sauce ever with 4tbs cream, 2oz cheshire cheese (has to be cheshire) and half a teaspoon of mustard powder.
Bloody luscious....i even licked the plate and got some on my nose