Carrots Onions Celery Mixture for Soups and More

A carrots, onions, and celery mixture is a simple sauté of finely chopped vegetables, often called mirepoix in French cooking. Cooked gently in oil or butter, it makes a savory, aromatic base for soups, stews, sauces, rice, and other dishes, while also working as a quick vegetable side.

Ingredients

1 cup finely diced yellow onion (about 150 g; 1 medium onion)
1 cup finely diced carrot (about 130 g; 1 medium-large carrot)
1 cup finely diced celery (about 100 g; 2 medium ribs)
1 tablespoon olive oil (15 ml), or unsalted butter
¼ teaspoon fine salt (about 1.5 g), plus more to taste
2 tablespoons water (30 ml), as needed to prevent sticking
⅛ teaspoon freshly ground black pepper (about 0.3 g), optional

Instructions

Prepare the vegetables. Peel the carrot and onion, then cut the onion, carrot, and celery into small, fairly even dice, about ¼ inch (6 mm). Even pieces cook at a similar rate. Pat the vegetables dry if they are wet from rinsing.
Warm the fat. Set a medium skillet or saucepan over medium-low heat. Add the olive oil or butter and let it warm until the butter has melted or the oil shimmers lightly, about 1 minute. It should not smoke.
Soften the vegetables. Add the onion, carrot, celery, and salt. Stir to coat, then cook uncovered for 12–15 minutes, stirring every couple of minutes. Adjust the heat so the vegetables soften gently without browning quickly. If the pan looks dry or the vegetables begin sticking, stir in the water 1 tablespoon (15 ml) at a time.
Check and season. The mixture is ready when the onion is translucent and the carrot and celery are tender but still hold their shape. Taste and add more salt or the optional black pepper. Use immediately as a recipe base, or serve it warm as a side.

Tips

Keep the dice consistent. Smaller pieces soften more quickly and blend into soups and sauces; larger pieces stay distinct and may need a few extra minutes. Aim for even cuts rather than exact uniformity.
Cook gently for a classic base. Mirepoix is usually softened, not deeply browned. High heat can darken the onion before the carrot is tender and make the mixture taste more roasted than sweet and mellow.
Use oil or butter according to the dish. Olive oil is a flexible choice for most savory recipes. Butter adds a richer flavor, but can brown if the pan is too hot; lower the heat if it starts to color.
Scale or prep ahead. Keep the same volume ratio—equal parts diced onion, carrot, and celery—for a larger batch. You can chop the vegetables up to a day ahead and refrigerate them separately or together in a covered container.

Serving Suggestions

For a recipe base, stir the cooked mixture into lentil, bean, chicken, or vegetable soup; add it to a stew with broth and other ingredients; or use it to start a tomato or pan sauce. It also brings savory depth to cooked rice, barley, couscous, and savory pie fillings. If a recipe calls for raw mirepoix, add this cooked mixture only when the recipe allows for pre-softened vegetables, since cooking changes both its texture and moisture.

To serve it on its own, spoon the warm vegetables beside roast chicken, baked fish, eggs, or a grain bowl. Finish with chopped parsley or a small squeeze of lemon if you want a fresher contrast. The mixture is gently seasoned so it can fit different dishes; adjust salt and herbs to match what you are serving.

Variations

French-style mirepoix: The classic French mixture uses onion, carrot, and celery, commonly in a 2:1:1 ratio by weight. This recipe uses equal volumes for an easy home-cooking measure; the more onion-forward ratio is useful when the vegetables will flavor a stock or long-cooked dish.

Italian soffritto: Add 1 tablespoon (about 10 g) finely chopped garlic near the end of cooking, and use olive oil. Some versions include herbs; add tender herbs near the end so their flavor stays noticeable. Regional and household versions vary.

Cajun or Creole-inspired base: Use 1 cup each (about 150 g, 130 g, and 100 g) of onion, celery, and green bell pepper instead of carrot. This is often called the “holy trinity” and gives dishes a more savory, peppery character than the sweeter carrot-based mixture.

Herb or spice variation: Add ½ teaspoon dried thyme (about 0.5 g) while the vegetables cook, or stir in 1 tablespoon (4 g) chopped fresh parsley at the end. For a richer, browned flavor, increase the heat slightly only after the vegetables have softened, and cook briefly while stirring.

Storage and Reheating

Transfer leftovers to a shallow, covered container and refrigerate within 2 hours of cooking. Keep them refrigerated at 40°F (4°C) or below and use within 3–4 days. For longer storage, freeze in a tightly sealed container or portioned freezer bag for up to 3 months for best quality. Thaw in the refrigerator or add frozen portions directly to a soup or stew.

Reheat only the amount you need in a skillet over medium-low heat, stirring until steaming hot; add a teaspoon of water if it seems dry. You can also microwave it in a covered, microwave-safe dish, stirring halfway through. When serving the mixture as leftovers, reheat to 165°F (74°C), as recommended for leftovers by USDA FSIS. If it is going into a dish that will be fully cooked, it can be added directly during that dish’s cooking.

Frequently Asked Questions

What is the carrots, onions, and celery mixture called?
In French cooking, onion, carrot, and celery cooked together as an aromatic base are called mirepoix. Similar vegetable bases have different names and proportions in other cuisines, such as soffritto in Italy and the onion-celery-bell pepper combination called the holy trinity in Cajun and Creole cooking.

What is the usual ratio for mirepoix?
A common French ratio is 2 parts onion to 1 part carrot and 1 part celery by weight. Equal-volume portions, as used here, are convenient for a small batch and give a balanced mixture. The best ratio can depend on the dish and personal preference.

Can I make this mixture without celery?
Yes. Use extra carrot or onion, or substitute diced fennel for some or all of the celery. Fennel has a mild anise-like aroma, so it will change the flavor; extra carrot makes the base sweeter, while extra onion makes it more savory.

Should mirepoix be browned?
Usually it is softened over low or medium-low heat rather than browned, especially when it will go into stock, soup, or a light sauce. Browning is fine when you want a deeper, roasted flavor, but keep stirring so the onion does not burn.

Can I use frozen chopped vegetables?
Yes, though frozen vegetables release more moisture and may become softer. Cook them from frozen over medium heat, allow excess water to evaporate, and then lower the heat to finish softening. The result is convenient for soups and stews but may be less distinct as a side dish.

Can I prepare a larger batch?
Yes. Multiply each ingredient by the same amount and use a wide pan or cook in batches. Overcrowding a small pan makes the vegetables steam unevenly and can extend the cooking time. Cool and refrigerate the extra promptly, or freeze it in recipe-sized portions.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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