The default mirepoix is 50% onion, 25% carrots, and 25% celery. They're chopped up and cooked at a moderate heat in a pan with some oil or butter. That's it. The result is astonishingly savory, and it can be used to flavor a soup or as part of a non-classic stir fry.
Wikipedia has it that the proportions are by weight, not volume, but I say that mirepoix is pretty forgiving about such things.
And it's pronounced meer pwah. I'd only heard the word, and I never would have guessed there was an x in it.
More about mirepoix-- my next mirepoix may well include mushrooms.
I thank dcseain for introducing me to mirepoix.
 The carnival is based on the premise that a lot of people are spending more than they need to on prepared food because they don't know how to get started on cooking, and in many cases don't have the money or other resources to have slack for much in the way of failed experiments.
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