All for one, one for all

WHAT could be more pedestrian -- and less glamorous -- than onions, carrots and celery? Yet mirepoix, the simple trinity of ordinary vegetables cut into even dice, forms the foundation of a tremendous number of dishes. Knowing how to make and use mirepoix is one of the essentials of classical French cooking. But it’s so important in all cooking that you’ve probably made it a thousand times without necessarily knowing it.

Sweat mirepoix in butter or olive oil, and it forms the basis of sauces, soups, risottos and braises. Cut into bigger cubes, the vegetables begin stocks or stews. Cut more finely, they start sauces or add flavor to roasts or soups. Diced and added at the end, they brighten braises or form their own garnish -- some cooks even add them twice, as a foundation and later, to refresh the flavors.

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Bare essentials

BASIC mirepoix, because it is so fundamental, acts almost literally as a foundation. It provides the ground floor for other layers -- beans in a soup, meat in a braise -- to build upon.

Carrots, onions and celery may be everyday vegetables, but they are also aromatics, which means they enhance the natural flavors and aromas of foods. By cooking them slowly together, you’re releasing these flavors and their liquids and creating a base for the dish.

Mirepoix is traditionally composed of 50% onions, 25% carrots and 25% celery. This ratio is important because aromatics, like most flavors, function proportionally. A 75% carrot ratio, for example, would make a tasty puree of carrot soup but a questionable flavor base.

You can vary the ingredients, adding garlic or shallots or fennel or ham, substituting parsnips for carrots to make the white mirepoix used in fish fumets (concentrated broths) or light stocks, adding lemon grass or chiles for regional cuisines. Classical French cooking uses butter, while Provencal cooking relies more on olive oil -- as does Italian and Spanish recipes. The cooking of Southwest France, on the other hand, uses duck or goose fat. Elsewhere in the world, you might find peanut oil or ghee.

French mirepoix is so essential that many cooking cultures depend on a variation of it: Italian food relies on soffrito, Portugal has refogado, Spanish cooks use sofrito, Indonesians have bumbu.

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Dice with precision

SO, how to cut it? Size matters. A lot.

In classical cooking, and in the boot camp sometimes called culinary school, mirepoix is cut finely, showcasing painfully exact cuts: brunoise (eighth-inch cubes) or macedoine (quarter-inch cubes). Though chopping vegetables into tiny dice may seem a bit excessive to the home cook, there is a reason to have nice cuts for your mirepoix. Uniformity of cuts means uniformity of cooking time, which is important.

How you cut a mirepoix varies from dish to dish and depends on such factors as the cooking technique you’ll use, the flavor desired and the length of cooking time.

A simple and relatively quick soup, such as a satisfying bean, duck and kale soup, calls for a medium-dice mirepoix because you want the vegetable pieces to be large enough to simmer without breaking apart but small enough to avoid upstaging the other ingredients. A long-simmering stew or braise would call for larger cuts, perhaps half-inch dice.

Dishes that are prepared quickly and use mirepoix for aesthetic reasons as well as those of taste usually call for very fine dice. Baked striped bass as well as chicken roulade call for very finely diced vegetables, which allows them to remain intact. It also makes for relatively simple presentation as the mirepoix can (in the case of the fish) become decoration and sauce, as well as the platform on which to bake the fish.

Chicken roulade has a similar simplicity, although it’s a bit more time consuming. Instead of wrapping the pounded chicken breast around the vegetables, which would be the technique of a traditional roulade, the vegetables are wrapped around the chicken -- the skin encases the mirepoix and holds it in place. In this dish, the mirepoix veers away from the classic, using bell peppers instead of carrots to reflect a Creole influence. (Onions, celery and bell peppers are New Orleans mirepoix because carrots were difficult to grow below sea level.) The proportions also vary slightly to showcase the colors as well as the flavors.

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How-tos of cutting

DOES cutting up mirepoix have to make you feel like an assembly-line slave? Not if you’re patient and follow a few helpful hints.

First, cut the onions in half lengthwise. Don’t cut off the stems, as they keep the layers together. Holding the onion half with the knuckles of your non-cutting hand, slice down horizontally in the desired increments. Next do the same thing, only vertically. When you’re done, most of the onion will be in uniform cubes.

The carrots and celery can’t be done like this (though garlic and shallots can). For carrots and celery, square the vegetables and, once you have straight edges, cut them into even blocks. You’ll have a lot of scraps, but that’s OK -- they can go into a plastic freezer bag for stock. Bell peppers are done similarly: Cut off the rounded edges and quarter them, then press the wedges flat. Depending on how small you want your dice, you can level the wedges horizontally.

Another way to save time -- and focus -- is to make mirepoix in large batches and freeze it, either raw or already sweated down, in smaller quantities just as you would other key ingredients such as stock or pesto.

So the next time a recipe calls for cutting up some onions and celery, consider the importance of the vegetables in front of you. They may not seem as exciting as the confit of Moulard duck or the whole fish you’ve just driven across town to buy, but they’re just as important.

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Flageolet bean, kale and duck soup

Total time: 2 hours, 20 minutes, plus overnight soaking

Servings: 6 to 8

Note: You may substitute small white beans such as cannellini or Great Northern for the flageolet beans. Duck confit is available at select Whole Foods markets, Surfas in Culver City and Nicole’s in South Pasadena.

1 cup dried flageolet beans

2 confit duck legs

3 parsley sprigs

3 thyme sprigs

2 bay leaves

5 black peppercorns

One medium onion, peeled

3 cups chicken broth, divided

1 bunch black kale (also called lacinato or cavolo negro), thick stems removed

1 cup (quarter-inch dice)

onions

1/2 cup (quarter-inch dice)

carrots

1/2 cup (quarter-inch dice)

celery

4 tablespoons duck fat (from confit), divided

3 garlic cloves, minced

Olive oil (if not enough fat)

1 teaspoon salt or more to taste

1/2 teaspoon freshly ground black pepper, plus more for baguette slices

16 slices French or sourdough baguette

1. Soak the beans in water overnight. The next day, when you’re ready to cook, first allow the duck confit to soften in the bag in a warm water bath or on a warm stove so it’s easier to pull apart and separate out the fat.

2. Wrap the parsley, thyme, bay leaves and peppercorns in cheesecloth and tie it with kitchen twine to make a bouquet garni. Drain the beans and put them in a medium pot with the bouquet garni and the onion and enough water to cover by about 2 inches.

3. Bring to a boil, then reduce the heat and simmer, skimming any froth, for about 1 1/2 to 2 hours, or until the beans are soft; add water if necessary to keep beans fully submerged. When the beans are cooked, remove the bouquet garni and the onion, discarding the bouquet garni and reserving the onion. Set the pan with the beans and cooking liquid aside. Place the onion in a blender with one-half cup chicken broth and one-half cup cooked beans. Process until smooth. Set aside.

4. Blanch the kale in lightly salted water, for about four minutes; drain, squeeze out the excess liquid and coarsely chop.

5. In a medium saucepan, cook the onions, carrots and celery together in 2 tablespoons duck fat over low heat until the vegetables start to soften, about 5 minutes. Add the garlic and cook 5 minutes more.

6. With a fork or your fingers, coarsely shred the duck and add it to the pot with the beans. Add the mirepoix (carrots-onions-celery mix), remaining chicken broth, kale, onion-bean puree and salt and pepper. Cover and simmer for 30 minutes (or longer) to combine flavors.

7. Brush the baguette slices with the duck fat, using olive oil if you run out of duck fat. Broil the slices until golden. Grind black pepper over the toasted slices. Divide the soup among serving bowls. Place two slices baguette on each serving.

Each serving: 312 calories; 16 grams protein; 38 grams carbohydrates; 9 grams fiber; 11 grams fat; 3 grams saturated fat; 33 mg. cholesterol; 655 mg. sodium.

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Striped bass with mirepoix

Total time: 1 hour

Servings: 2

Note: You can substitute any whole, firm, round fish; figure 1 pound whole fish per (half-pound) serving.

1 (1- to 2-pound) whole striped bass, gutted and scaled

Sea salt

Black pepper

1 cup (eighth-inch dice) onions

1/2 cup (eighth-inch dice) carrots

1/2 cup (eighth-inch dice) celery

1 tablespoon fresh thyme leaves

2 cloves garlic, minced

2 tablespoons extra virgin olive oil

1 cup dry white wine, divided

2 tablespoons cold unsalted butter

1 teaspoon minced fresh herbs (such as parsley or chives) for garnish

1. Heat the oven to 400 degrees. Rinse, dry and season the fish with salt and pepper. With a sharp knife, score the fish, three or four times per side.

2. In an ovenproof saute pan (with a lid that fits) large enough to accommodate the fish, cook the onions, carrots and celery in the olive oil over low heat for about 10 minutes, until crisp-tender and fragrant. Add the thyme and garlic, and cook about 5 minutes more, until the vegetables are tender.

3. Place the fish on top of the vegetables, then add three-fourths cup wine. Bring the wine back to a simmer, then cover the pan and put it in the oven. Bake until the fish is cooked through, about 15 to 20 minutes.

4. Remove the pan from the oven and gently remove the whole fish to a platter, leaving the mirepoix in the pan. To make the sauce, add the remaining quarter-cup wine and place the pan on the stove top over medium-low heat. Whisk or swirl the butter into the mixture until the butter has melted. Add salt and pepper to taste.

5. Spoon the sauce around the fish. Sprinkle with fresh herbs. Serve whole or fillet at the table.

Each serving: 485 calories; 35 grams protein; 13 grams carbohydrates; 3 grams fiber; 29 grams fat; 10 grams saturated fat; 104 mg. cholesterol; 175 mg. sodium

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Chicken roulade with bell pepper mirepoix

Total time: 1 hour, 30 minutes

Servings: 4

Note: This recipe uses the skin from 4 whole chicken breasts but the meat from 2. Reserve the leftover meat for another use.

4 boneless skin-on whole chicken breasts

1 teaspoon salt

1/4 teaspoon freshly ground black pepper

1/4 teaspoon dried basil

1/4 teaspoon dried thyme

1/8 teaspoon paprika

1/8 teaspoon cayenne

1/4 cup plus 2 tablespoons

extra virgin olive oil, divided

1 cup (eighth-inch dice)

onions

1/4 cup (eighth-inch dice)

celery

1/4 cup (eighth-inch dice) green bell pepper

1/4 cup (eighth-inch dice) red bell pepper

1/4 cup (eighth-inch dice) orange bell pepper

1/4 cup minced shallots

6 sprigs fresh thyme

1 cup dry white wine

1/4 cup ( 1/2 stick) cold unsalted butter

2 teaspoons chives, snipped into small pieces using kitchen shears.

1. Carefully remove the skin from the chicken breasts, keeping the 4 skins intact, trim excess fat and reserve. Cut the breasts in half -- you’ll have 8 pieces total -- and set aside 4 for another use. Place a piece of plastic wrap on top of each piece of chicken and, using the flat side of a meat tenderizer, pound the 4 half-breasts flat, to about a quarter-inch thick.

2. In a small bowl, mix the salt, pepper, basil, thyme, paprika and cayenne. Sprinkle this seasoning mixture equally over the 4 flattened breasts. Roll the breasts to form 4 logs and set aside. Heat the oven to 350 degrees.

3. Meanwhile, add one-fourth cup olive oil to a medium (10-inch) ovenproof saute pan over low heat. Add the mirepoix (onions, celery and green, red and orange peppers). Cook until tender, about 10 minutes.

4. Spread out each chicken skin, outside of the skin down, spoon one-fourth of the mirepoix from the pan over the skin and then place a rolled chicken breast on top of the vegetables. Roll the skin around the chicken, being sure to encase the vegetables evenly. Tie the roulade, about four times, with kitchen twine. Repeat with each skin.

5. Add the remaining 2 tablespoons olive oil to the pan and sear the roulades over medium high heat until you get good color (about 7 to 8 minutes).

6. Transfer the pan of roulades to the oven and roast until cooked through, about 20 minutes, turning the roulades occasionally so they brown evenly.

7. Remove the pan from the oven, transfer the roulades to a cutting board and let them rest. Pour out excess fat. On the stove top over medium heat, add the shallots to the pan and quickly brown them, about 1 to 2 minutes. Add the thyme sprigs. Deglaze with the wine and reduce to one-fourth cup, about 6 to 8 minutes, over medium high heat. Strain the sauce into another pan.

8. Cut each roulade on the diagonal and fan out the pieces on serving plates. Heat the sauce over medium heat to just a simmer. Add the butter and swirl until combined, adding a little salt to taste if needed. Spoon sauce around the sliced roulades and garnish with chives.

Each serving: 588 calories; 37 grams protein; 7 grams carbohydrates; 1 gram fiber; 41 grams fat; 13 grams saturated fat; 133 mg. cholesterol; 245 mg. sodium.