Soupe aux Rognons

Ingredients

Equipment Needed

• •4-quart heavy saucepan
• •12-inch heavy skillet
• •Fine-mesh sieve
• •Sturdy whisk
• •Instant-read thermometer

Instructions

1. 1

   Trim and dry kidneys

   Pull away the thin outer membrane from the kidney, separate the lobes if using calf's kidney, and cut out every firm white tube and piece of central fat. Cut the cleaned kidney into large dice about 3/4 inch (2 cm) across, or into thick slices. Blot it very dry and keep it chilled while the soup is made. Moisture prevents browning, while the white core remains tough however carefully you cook it.

   Fresh kidney smells clean and mineral, not sharply ammoniacal. Trimming corrects texture, but it cannot repair poor freshness; return a kidney with an aggressive ammonia smell.
2. 2

   Cook the roux brun

   Melt the 6 tablespoons of butter in a heavy saucepan over medium-low heat. Whisk in the flour, then cook for 15 to 20 minutes, stirring steadily across the floor and corners, until the roux is evenly chestnut-brown and smells of toasted hazelnuts. Patience is the soup here. A pale roux leaves a raw, floury taste; if you see black flecks or smell bitterness, begin again, because scorched flour cannot be hidden under stock or Madeira.

3. 3

   Moisten without lumps

   Take the saucepan off the heat. Reserve 1 cup of the stock, then whisk about 1 cup into the roux a little at a time, making a completely smooth, loose paste before adding the remaining stock in a steady stream. The roux may seize at first. Keep whisking. If lumps form, do not pour it out. Ça se rattrape: whisk vigorously off the heat or blend briefly with an immersion blender, then rely on the final straining to catch anything stubborn.

   Adding the first stock gradually is what keeps the roux smooth. Once that initial paste is even, the remaining liquid can go in much more quickly.
4. 4

   Simmer and strain

   Return the saucepan to medium heat and bring the soup slowly to a bare simmer, whisking along the floor until it begins to thicken. Lower the heat and simmer gently for 35 minutes, stirring occasionally and skimming away surface foam. The finished base should lightly coat the back of a spoon and taste of stock and toasted roux, never raw flour. Pass it through a fine-mesh sieve into a clean saucepan, adjust the consistency with as much reserved stock as needed, and season cautiously with salt and white pepper. Hold it at the gentlest simmer.

5. 5

   Sear the kidney briskly

   Heat a wide skillet over medium-high heat and add the remaining 2 tablespoons of butter. When the foam subsides, add the kidney in two uncrowded batches and toss briskly until bronzed outside and just cooked through, about 3 to 4 minutes for dice or 45 to 60 seconds per side for slices. The center of the thickest piece should reach 160°F (71°C). Season only after searing. If the pan fills with grey liquid, lift the kidney out immediately, pour away the liquid, wipe and reheat the pan, then finish in smaller batches with a little of the remaining butter. Ça se rattrape.

   Do not simmer the seared kidney in the soup. Prolonged cooking makes it firm and sends its mineral flavor through the whole pot.
6. 6

   Finish with Madeira

   Take the soup off the heat and stir in the Madeira. Taste once more for salt and white pepper, but do not boil after adding the wine or its perfume disappears. Divide the butter-seared kidney among warmed bowls, pour the soup over it, and serve at once. The kidney stays tender, the roux gives quiet body, and the Madeira arrives last. À table!

Chef Tips

• •Calf's kidney is broad, lobed, and relatively mild; sheep's kidneys are smaller, firmer, and more assertive. Both belong in the source preparation. What matters most is freshness, thorough trimming, and a very dry surface before searing.
• •Use an unsalted stock with a clean beef or veal flavor. A heavily salted carton becomes punishing as the soup simmers, while a weak stock leaves the roux carrying more weight than it should.
• •Do not add cream. This soup gets its body from the roux brun, and cream would soften the precise contrast between toasted stock, kidney, and Madeira.
• •Choose medium-dry Madeira rather than salted cooking wine. It should smell of toasted nuts and dried fruit, and it goes into the soup off the heat so those aromas reach the table.

Advance Preparation

• •The strained soup base can be prepared through step 4 up to 48 hours ahead. Cool it promptly, cover and chill, then return it to a bare simmer before finishing with freshly seared kidney and Madeira.
• •The kidney can be trimmed and cut up to 4 hours ahead, then kept covered and chilled between clean towels. Do not sear it ahead; that final brisk cooking is the dish, not brigade scaffolding.
• •Freeze the strained base without the kidney or Madeira for up to 1 month. Thaw and whisk it over gentle heat, loosening with stock if necessary, then complete the final two steps.

Frequently Asked Questions

Nutrition Information

1 serving (about 240g)