Mirepoix (pronounced "meer-pwah") is a combination of chopped carrots, celery and onions used to add flavor and aroma to stocks, sauces, soups and other foods.
These three ingredients are commonly referred to as "aromatics." Cajun cooking uses a variation on mirepoix which consists of three parts onions, two parts celery and one part green bell pepper.
Other variations utilize parsnips, leeks, celery root, fennel bulb, shallots or garlic.
Traditional mirepoix consists of two parts onions, one part carrots and one part celery, with the proportions determined by weight. Therefore, one pound (16 oz) of mirepoix would take 8 ounces of onions, 4 ounces of carrots and 4 ounces of celery.
And if you're in culinary school, then by all means break out the scale. For that matter, do whatever your instructor tells you to do.
But if you're cooking at home, you can feel free to eyeball it. I do believe in using the scale for certain things, especially when it comes to measuring flour. But mirepoix is not something that needs to be calibrated to the precise gram. You could even use volume measurements (like two cups onions, and one cup each of carrots and celery) instead of weight.
[Also see: How to Make Chicken Stock]
When you're making stock, the mirepoix is ultimately strained out, so you don't need to be particularly precise when chopping the vegetables.
The pieces should be more or less uniform in size, however, to allow for uniform cooking times.
The more finely mirepoix is chopped, the more quickly its flavor and aroma is released into a stock. Since brown stock is simmered longer than white stock, it's perfectly acceptable to cut the mirepoix into pieces an inch or two in size.
For white stock, a ½-inch dice is probably best.
Making Stock with Mirepoix
For brown stocks such as beef stock, use a pound of mirepoix per 6 quarts of cold water. It's customary to roast the mirepoix before adding it to the stock liquid, which contributes flavor and color to the finished stock.
For white stocks such as chicken stock or veal stock, use about a pound of mirepoix for 5 quarts of cold water. For fish stock, use half a pound of mirepoix per gallon of cold water. You can cook the mirepoix and fish bones in butter for a few minutes before adding the water.
- Leeks can be used in place of some or all of the onions.
- If you want a colorless stock, you can make a "white mirepoix" by substituting parsnips, mushroom trimmings, or both, for the carrots, or just omitting the carrots altogether.