Roast tenderloin of beef with shallot and porcini mushroom sauce

Remove the silver skin with a thin sharp knife without cutting into the meat; leave the chain attached; trim external fat.

Tie one end with butcher's string, then loop the string over the loin and cinch it every inch or two; run the string under the bottom and tie off where it started.

Soak dry porcini in water until soft, about an hour (faster in warm water); squeeze out, chop bite-size, and reserve the water.

Season the beef very generously with salt and black pepper; sear well on all sides in a little vegetable oil in a heavy skillet on medium-high to high for a brown crust and a fond.

Remove the beef; turn the heat to medium, add a chunk of butter, lots of shallots and a pinch of salt; cook 5 or 6 minutes until golden brown, letting their liquid lift the fond.

Deglaze with tarragon vinegar; let it evaporate; add chicken stock, the porcini, salt and pepper, a splash of heavy cream and a big splash of strained mushroom water.

Return the beef to the sauce and roast at 325 until the internal temperature reaches 125, about 45 minutes.

Rest the beef under loose foil at least 10 minutes.

Boil the sauce to the wanted consistency; off the heat, add salt, pepper, a chunk of cold butter and a big pinch of fresh tarragon.

Cut off the string; serve whole on the sauce or sliced on top of it.