Mirepoix is a simple combination of onion, celery and carrot sautéed together. It is so common in French cooking that recipes will sometimes call for a certain amount of mirepoix, instead of listing the three vegetables separately.
When you do see recipes for the mirepoix, it is typically either two parts celery to one part each of onion and carrot, or equal parts each. I have found that you don’t have to be really precise with this. As long as there’s enough of each that you get all three flavors, and you dice everything about the same size, you’ll be good.
1 medium onion — the size of your fist
6-10 carrots — as big as your thumb at the base
2-3 celery stalks
It’s best to do this as mise en place. That’s just French for “set in place” — meaning get everything prepped and set out all at once before you start actually cooking. Set out three bowls before you start chopping.
First dice the onion.
Then do the celery. The bottom inch or so will be bright white, and quite possibly not looking very good.
That’s okay, since we’re going to cut the whole bottom off anyway.
Unlike onion, which grows underground but is completely clean after peeling the outside, celery grows aboveground and manages to accumulate lots of dirt in the bottom of the bunch.
Separate all the stalks and clean well with cold water. If it’s exceptionally dirty, put a capfull of distilled white vinegar in a sink full of cold water and rinse it there. Pat the clean stalks with a paper towel to dry them.
You can see above that the color can vary quite a bit from the outside to the inside. Keep the small leafy stems from the inside to go in your Bloody Mary and dice up the larger pieces.
Cut each one lengthwise before dicing one or two stalks together.
For the carrots, don’t get those little pre-milled, suppository shaped things they market to kids. Get real, carrot-shaped carrots. Cut off the leafy top, and also the stringy root at the smaller end.
Chop longer pieces from the smaller end, and thinner pieces from the big end.
Clean up as you go, putting all the trimmed pieces in the trash, and the diced pieces into the bowls you set aside at the beginning.
Sauté everything together in a little melted fat — bacon, lard or butter.