Potage Saint-Marceau

Ingredients

Equipment Needed

• •4-quart heavy saucepan
• •1-quart saucepan with lid
• •Countertop blender with vented lid
• •Fine-mesh sieve
• •Heatproof measuring jug

Instructions

1. 1

   Cut the garnish

   Split the leek white lengthwise and wash carefully between the layers. Cut it into 1-inch sections, flatten them, and slice them into the finest julienne, match-shaped strips. Measure exactly 3 tablespoons after cutting. Pick 1 tablespoon of chervil pluches, the small tender leaves and fine shreds, and keep them cool beneath a barely damp towel.

   The finished two-quart potage receives 4 tablespoons of garnish in total, preserving the source proportion of 2 tablespoons per quart.
2. 2

   Étuver the leek

   Melt 1 tablespoon of the butter in a small covered saucepan with 2 tablespoons taken from the measured cold water and a pinch of the salt. Add the leek and étuver, cook gently under the lid without browning, for 4 to 5 minutes, until supple but still distinct. If the pan dries before the leek is tender, add another teaspoon of water. Spread the leek on a plate so it stops cooking; the chervil remains raw until the finish.

3. 3

   Cook peas briefly

   Pour the remaining cold water into a 4-quart saucepan, add all but a final pinch of salt, and bring it to a full boil. Add the peas, cover only until the boil returns, then uncover and cook until a pea crushes easily between two fingers while remaining vividly green, 3 to 4 minutes for frozen peas or 5 to 7 minutes for fresh ones. Drain immediately over a heatproof bowl and reserve every drop of the cooking water; leaving tender peas sitting in the hot water only dulls their flavor and color.

   Taste a pea rather than trusting the clock. Young fresh peas may cook as quickly as frozen ones, while large mature peas need another minute.
4. 4

   Purée and pass

   Working in batches no more than half full, blend the peas with 4 cups of their reserved cooking water until completely smooth, 60 to 90 seconds. Vent the blender lid and cover the opening loosely with a folded towel so pressure cannot build. Add more reserved liquid in small amounts when needed to keep the purée moving. Pass it through a fine-mesh sieve, pressing firmly and scraping the silky purée from the underside. Return it to the large saucepan and bring it to a bare simmer. If it pours thinly like broth, reduce it gently before adding butter; if it mounds on the spoon, loosen it with reserved cooking water or the optional hot water. Adjust the finished volume to about 8 cups.

5. 5

   Monter au beurre

   Once the purée coats a spoon in a thin, even film, remove it from the heat. Monter au beurre by whisking in the remaining 5 tablespoons of cold butter in three additions, letting each disappear before adding the next. Stir in all 3 tablespoons of cooked leek julienne and the tablespoon of chervil pluches. If oily specks rise to the surface, the soup became too hot. Take it off the heat and blend in 1 tablespoon of hot water, adding a second only if necessary. Ça se rattrape. Once the butter is in, never let the potage boil.

6. 6

   Ladle at once

   Taste and correct the salt. Warm the serving bowls with hot water, dry them, and stir the potage once so the leek and chervil are evenly distributed before ladling. Serve immediately while the butter emulsion is glossy and the chervil still tastes fresh. À table!

Chef Tips

• •Frozen peas are the honest choice outside the brief fresh-pea season. They were picked while sweet and tender; a tired fresh pea with a starchy skin brings nothing noble to the pot.
• •Chervil is part of the identity, not a decorative flourish. Parsley makes a respectable pea soup, but it does not make Potage Saint-Marceau; the chervil's soft anise note is what lifts the butter and leek.
• •Use water here, not a strongly flavored commercial stock. The source is built on an ordinary pea purée, and water lets the peas remain the foundation instead of making the soup taste chiefly of someone else's broth.
• •Use cultured unsalted butter if you have it and ordinary unsalted butter if you don't. Butter, not margarine; the final emulsion provides the gloss and roundness. We don't apologize for butter.
• •For a dinner party, pour a dry Sauvignon Blanc from the central Loire. Its freshness suits the peas and chervil, while its acidity clears the butter from the palate.

Advance Preparation

• •The pea base can be cooked, blended, and strained up to 24 hours ahead. Stop before adding the finishing butter and garnish, cool it promptly in a shallow container, cover, and refrigerate.
• •The leek julienne can be étuvée up to 6 hours ahead and refrigerated. Pick the chervil shortly before serving so its leaves remain fresh and fragrant.
• •Reheat the prepared base gently, set its consistency, and only then monter au beurre. Finished leftovers keep for 2 days in the cold; warm them without boiling and blend in a spoonful of water if the butter sheen has separated.

Frequently Asked Questions

Nutrition Information

1 serving (about 320g)