Filet de Bœuf Duchesse

Ingredients

Equipment Needed

• •Narrow metal skewer and blunt-ended chopstick
• •Kitchen twine
• •Lidded casserole sized closely to the fillet
• •Wide 2-quart saucepan for the reduction
• •4-quart pot for the potatoes
• •Potato ricer or food mill
• •Large piping bag with a ¾-inch star tip
• •Parchment-lined broiler-safe sheet pan
• •Instant-read thermometer
• •Long serving platter and sauceboat

Instructions

1. 1

   Lard and tie

   Keep the beef and back fat cold. Working from each cut end, pass a narrow metal skewer lengthwise into the fillet to make four evenly spaced channels, stopping around the middle. Push one firm baton of back fat into each channel with the blunt end of a chopstick, then repeat from the opposite end. Tie the fillet at 1½-inch intervals so its thickness remains even. Season it with 1 teaspoon of the salt and ½ teaspoon of the pepper, then leave it out for 30 to 40 minutes while you begin the potatoes and sauce foundation.

   A butcher can lard and tie the fillet for you. If you do it yourself, chill the fat until rigid enough to push cleanly; soft fat smears instead of passing through the meat.
2. 2

   Reduce the stock

   If the stock does not set softly when cold, bloom the gelatin in 2 tablespoons of the measured cold stock for 5 minutes. Bring the remaining stock to a lively simmer in a wide saucepan and reduce it to about 1¼ cups (300 ml), skimming away any grey foam but keeping every bit of clean brown flavour. Whisk in the bloomed gelatin, if using, and hold the reduction over the gentlest heat. This measured reduction is the home equivalent of the brown stock and half-glaze a saucier once kept ready.

3. 3

   Dry the potatoes

   Cover the potatoes with cold water by an inch and add 1 tablespoon of the salt. Bring to a boil, lower to a steady simmer, and cook for 18 to 22 minutes, until a knife passes through without resistance. Drain thoroughly, return them to the hot pot, and shake them over low heat for 2 to 3 minutes. Stop only when the surfaces look floury and a pale starch film appears on the pot. Water is the enemy here; this drying is what lets pommes Duchesse hold their ridges.

4. 4

   Pipe pommes Duchesse

   Pass the hot potatoes through a ricer or food mill into the dry pot. Fold in the softened butter, the remaining 1 teaspoon salt, the remaining ½ teaspoon pepper, and the nutmeg without beating. Let the purée cool for 2 minutes, then work in the yolks one at a time until smooth and firm. Spoon it into a piping bag fitted with a large star tip and test one rosette on a parchment-lined sheet. If it slumps, the mixture is too warm: scrape it back into the bag and chill for 10 minutes. If it is too stiff to pipe, work in 1 teaspoon of the beaten egg. Ça se rattrape. Pipe 12 generous rosettes, then brush their ridges lightly with the remaining egg.

5. 5

   Poêle the fillet

   Set up the home-scale Poëlings (No. 250) exactly as that preparation directs, using a lidded casserole only a little larger than the fillet. Cook the beef unmoistened as prescribed and begin checking its centre after 25 minutes. Insert an instant-read thermometer through one cut end: remove the fillet at 120 to 122°F (49 to 50°C) for a rosy medium-rare after resting, or at 128°F (53°C) for medium. Rest it loosely tented for 15 to 20 minutes. Do not glaze it yet; the glaze belongs to the last moment.

   Time can only estimate a fillet because thickness matters more than weight. The thermometer protects an expensive cut and lets you give the rest of your attention to the potatoes.
6. 6

   Brown the potatoes

   While the beef rests, heat the oven to 425°F (220°C). Bake the pommes Duchesse for 10 to 14 minutes, until set and pale gold, then place them under the broiler for 30 to 90 seconds to colour their ridged edges. Watch without wandering; the difference between burnished and burnt is one conversation. If one side colours first, rotate the sheet rather than leaving the potatoes under longer.

7. 7

   Finish the half-glaze

   Bring the reduced stock back to a simmer, add the Madeira, and reduce until about 1 cup (240 ml) remains and the demi-glace au Madère coats the back of a spoon in a clear, glossy layer. Taste before adding salt because reduction concentrates it. Take the pan off the heat and whisk in the cold butter a few cubes at a time. If the butter separates into an oily rim, whisk in 1 teaspoon of cold water away from the heat. Ça se rattrape. If the sauce is thin, reduce it a little longer; if it has tightened too far, loosen it with a spoonful of stock.

8. 8

   Glaze and arrange

   Warm a long serving platter and a sauceboat. Brush the rested fillet with a thin, shining coat of the hot demi-glace au Madère, then set it whole along the platter and surround it closely with the browned pommes Duchesse. Pour the remaining sauce into the sauceboat and send it separately, as the dish requires. Present the fillet whole, then carve it across the grain into eight thick slices at the table. À table!

Chef Tips

• •Ask for the centre section of the tenderloin, evenly thick from end to end. The taper cooks too quickly and the head too slowly; uniform shape is more valuable here than an impressive weight.
• •Unsmoked pork back fat enriches the lean fillet without imposing a bacon flavour. Keep the batons very cold, and ask the butcher to lard the meat if you would rather leave the threading to practiced hands.
• •Choose stock that tastes of roasted bones and meat, not salt or yeast extract. If it turns softly gelatinous in the cold, omit the powdered gelatin; reduction will supply all the body the sauce needs.
• •Use dry Madeira from a bottle you would drink. Bottles labelled cooking wine are usually salted, and reduction makes that salt louder. A Médoc or a Cabernet Franc from the Loire sits beautifully beside the finished dish.
• •Refrigerate leftovers within 2 hours. The beef keeps for 3 days and is best sliced cold or warmed very gently; the pommes Duchesse keep for 2 days and regain their edges in a 375°F (190°C) oven.

Advance Preparation

• •Lard and tie the fillet earlier on the day of serving, then refrigerate it uncovered on a tray. Season it and bring it out 30 to 40 minutes before cooking.
• •Reduce the brown stock up to 2 days ahead and refrigerate it. Reheat it before adding the Madeira; finish with cold butter only when the sauce is ready to serve.
• •Pipe the pommes Duchesse up to 6 hours ahead. Chill them uncovered until firm, then cover lightly; brush with beaten egg just before baking.
• •The finished sauce may wait for 20 minutes in a warm spot, but do not let it boil after the cold butter goes in. Whisk it briefly before filling the sauceboat.

Frequently Asked Questions

Nutrition Information

1 serving (about 500g)