(This is a c&p from an old blog entry - pls excuse the somewhat florid style...)
A couple of big handsful of mushrooms
3 garlic cloves
1 yellow onion
1 stick of celery
1.Take a big pan, put it on a low-to-middling heat. Add a generous lump of butter, and a good glug of olive oil. Let them warm and ooze and mingle together until just beginning to bubble.
2. Peel three garlic cloves (cloves, NOT bulbs - you'd be amazed how often people mistake the two...), squish them a bit by putting them under the flat side of a knife and bashing down, and then add to the pan.
3. Finely chop a girl-fist sized yellow onion, and add when a delicate scent of roasting garlic begins to gently and deliciously assail your nostrils.
4. Finely chop a stick of celery, and add when the onion is just on the verge of becoming transparent. Stir together, and spend a moment reflecting on the fact that there are few nicer smells in the world than that of frying onions.
5.Add a few generous grinds of black pepper.
Under no circumstances should you allow anything in the pan to colour - nice and translucent is what we're going for here.
6. Take some mushrooms - common-or-garden white champignon style ones do very well, but I'm sure you could probably choose something more exotic should you so wish. I generally reckon on 6 or so champignons, about the size of the gap between thumb and forefinger when making an OK sign, per person. Do whatever it is you usually do to clean the mushrooms - wash, brush, or in my case, peel. Or just enjoy the extra texture that clods of mushroom soil bring to the dish. Whatever. Break the mushrooms into appetising-looking bits (I remember once reading in a cookbook that one should never slice mushrooms - it lets too much of the yummy juice out apparently - but I have no idea whether breaking is actually better than chopping. Personally, I just find chunks more visually attractive than slices. Also mushroom flesh is stupendously, almost indulgently, tactile, and deserves more attention than can be lavished upon it by the blade of a knife. And mushrooms make a great sort of popping noise when you break them in half. Never underestimate the power of all five senses when cooking) and add to the pan when the mixture therein has reached the stage where it warrants being called 'goey'.
Note: mushrooms suck up an inordinate amount of grease while cooking - so it might be worth throwing in another lump of butter. More pepper might be good at this point too.
7. If you poke about in the pan, you'll see the cloves of garlic you put in at the start, lovely and soft and golden and gooey. Fish them out, chop them up, and return to the pan. This might seem a bit of a round-about, not to mention messy, way of getting chopped garlic into a dish, but I've found that if I just chop it up right at the start the little bits tend to fry too hard and get a bit bitter, and I much prefer the gentle, almost roasted flavour, of letting them cook whole. And anyway, cooking's no fun if it isn't messy. If you're not a big garlic fan, just fish 'em all out and discard - they'll have had enough time in the oil to give a subtle kiss of flavour.
8. Add a pinch of ground nutmeg.
9. Pestle and mortar ahoy. Grind up and add about 3 allspice corns. Allspice has a wonderful, pungent, warming flavour, but it can be a bit overpowering - best to add in increments.
10. Put the kettle on. Get a mug and a stockcube (pick a flavour, any flavour, although probably not fish) and stand it upright on its narrow end in the cup. Add boiling water to just cover. Add to the pan when the mushrooms are beginning to turn a tiny little bit golden. Stockcubes are generally salty enough to banish the need for extra salt. Up to you, though.
11. Parsley. There is no such thing as too much parsley. Either chop up the hugest bunch of fresh parsley you can find, or about half a packet of the pre-chopped frozen stuff works just as well. Chuck in pan.
12. At the point when the mushroom juice and melty butter and stock are making a shallow sea of wonderous liquid in the pan, add some cream - proper cooking cream if you're fortunate enough to be in a country which sells such finesses, ordinary single cream if you're not. How much is again up to you, a dash will add enough creamy flavour to warrant its presence if you prefer a lighter sauce, or just keep on pouring if you're in decadent mood.
13. Put the pasta on to boil in salted water. The 5 minutes or so of cooking time should be just right for the sauce to reduce down to a consistency you like the look of, and if it starts getting too thick, rest secure in the knowledge that you can always add a bit more stock or a bit more cream if the situation should so demand.
Considering the huge volume of ingredients you started out with, the amount of what have turned out to be the-incredible-shrinking-ingredients now left in the pan is probably begging the response, "Is that it?", but trust me, the sauce is impressively flavourful, and you don't actually need that much per plate of pasta.
14. At the last moment, stir in a couple of dashes of Balsamic vinegar. And now taste the sauce, if for some reason you've neglected to do so before. Add a bit of something or other if you think it necessary, then serve with an arty sprinkling of fresh parsley if you're into presentation, and the best Parmigiano cheese you can afford.