Mirepoix — onion, celery, and carrot, diced and cooked gently in fat — is the opening move of half the great dishes of Western cooking. Soups, stews, braises, stocks, sauces: look at step one and you will usually find these three vegetables. Learning to cut mirepoix properly is less about beauty (it usually melts invisibly into the dish) and more about uniformity: pieces the same size cook at the same rate, which is the difference between a sweet, even foundation and one that is half-scorched, half-raw.
The Classic Ratio
Commit this to memory: 50% onion, 25% celery, 25% carrot — two parts onion to one part each of the others. Onion provides the sweet base, celery the aromatic backbone, carrot the color and earthy sugar. Measure by weight or simply eyeball it: one large onion, three stalks of celery, one carrot lands you close.
Cutting Each Vegetable
Celery first: halve the stalks, then cut them into long strips — a julienne — and gather the strips to dice crosswise. Strings and all, celery is the easiest of the three.
For the carrot, peel it and trim the ends, then slice a thin flat off one side so it sits stable on the board instead of rolling under your knife. Cut planks, then strips, then dice. That first flattening cut is the single best knife-safety habit you can build.
The onion: peel, halve through the root, and lay each half flat. Slice from top to root without cutting through the root end — it holds the layers together — then slice crosswise and the onion falls into even dice.
What Size Dice?
Match the cut to the cooking time. Quick soups and sautés: small dice, about ¼ inch. Standard soups and braises: medium, about ½ inch. All-day stocks and stews: large chunks, since they have hours to give up their flavor. Whatever size you choose, keep all three vegetables consistent with each other.
Cook It Low and Slow
Mirepoix is sweated, not seared: medium-low heat, olive oil or butter, a pinch of salt to draw moisture, and 8–10 patient minutes until soft, translucent, and sweet. Color is optional — browned mirepoix suits dark stews and gravies, blond mirepoix suits light soups like my chicken vegetable avgolemono or potato leek soup.
Cut a big batch on Sunday and refrigerate it in a sealed container for 3–4 days of head starts, or freeze portions flat in bags for months — frozen mirepoix goes straight into the hot pan.
FAQ
Do I have to peel the carrot?
For long-simmered dishes, a well-scrubbed carrot is fine unpeeled. For refined soups and sauces, peel — the skin can bring a faint bitterness.
What is the Cajun “holy trinity”?
The same idea with bell pepper replacing carrot — the base of gumbo and jambalaya. Italian soffritto is another cousin, often with garlic and cooked further in olive oil.
Can I use a food processor?
You can pulse carefully, but it bruises the onion and makes everything weep juice. For most cooking it is acceptable; for the best texture, the knife wins.
Recipe Card
How to Cut Mirepoix
Instructions
- Cut celery in half then cut into long strips (julienne). Turn vertical and cut into desired dice.
- Peel carrot, cut ends off. Slice a slim piece of carrot turn on top flat side and slice into 1/4 inch Batonnet. Lay flat cut into julienne strips, then turn vertical cut into desired dice.
- Peel onion cut into half. Slice onion from top to bottom following up and down onion lines. Holding sliced onion together turn vertical and cut into desired dice.
- Mirepoix ratio is usually Onion 50% Celery 25% Carrot 25%