Beef Wellington

Pasos

1. Take the tenderloin out of the fridge 30 minutes before you start. Pat it very dry with paper towels, tuck the thin tip under if needed to get an even cylinder, and tie it with kitchen twine every 1 1/4 inches (3 cm). Season all over with the fine salt and pepper.
2. Heat the oil in a large stainless or cast-iron skillet over high heat until it just begins to smoke. Sear the beef for 1 minute per side, turning it along its whole length, then press each end against the pan for 30 seconds: the crust should be deep brown everywhere while the inside stays raw. Move it to a rack, remove the twine and immediately brush the whole surface with English mustard. Let it cool, then refrigerate for 20 minutes. Keep the skillet unwashed.
3. For the duxelles, very finely chop the mushrooms (by knife or by pulsing in a food processor, without turning them to paste), 2 of the shallots and the garlic. Melt 1 1/2 tablespoons (20 g) butter in a large sauté pan over medium heat, soften the shallots and garlic for 2 minutes, then add the mushrooms, the leaves from 3 thyme sprigs and a pinch of salt. Cook over medium-high heat for 12 to 15 minutes, stirring often, until all the released water has evaporated, a spoon dragged across the bottom leaves a dry trail and the mixture starts to sizzle. Spread on a plate and cool completely.
4. Lay two overlapping 20 inch (50 cm) sheets of plastic wrap on the counter. Arrange the prosciutto slices, overlapping, into a rectangle large enough to wrap the beef. Spread the cold duxelles in a thin, even layer over the prosciutto. Set the beef on the edge closest to you, roll it up tightly using the plastic wrap, then twist the ends like a candy wrapper to compact the log. Refrigerate for 30 minutes.
5. Roll the puff pastry between two sheets of parchment into a rectangle 1/8 inch (3 mm) thick, large enough to wrap around the beef with a 3/4 inch (2 cm) overlap. Beat the egg yolks with the milk. Unwrap the log, set it in the center of the pastry, brush the edges with egg wash, then fold the pastry over, trimming the excess so the overlap is only a single layer. Fold the ends like a parcel, trim what sticks out, and turn it seam side down onto a parchment-lined baking sheet. Refrigerate for 20 minutes.
6. Preheat the oven to 425°F (220°C), conventional bake, with a second baking sheet inside to heat up. Brush the Wellington all over with egg wash, score a light crosshatch with the back of a knife without cutting through, and sprinkle with flaky salt.
7. Slide the Wellington's sheet onto the hot sheet and bake for 30 to 40 minutes. Start checking at 30 minutes with a thermometer in the center: pull it at 118 to 122°F (48 to 50°C) for medium-rare. If the pastry browns too quickly before it reaches temperature, tent it loosely with foil.
8. While it bakes, make the sauce in the searing skillet. Melt 2 teaspoons (10 g) butter over medium heat, add the last shallot, chopped, and the last thyme sprig, and soften for 2 minutes while scraping up the browned bits. Pour in the red wine and reduce by two thirds, about 8 minutes. Add the beef broth and reduce by half again, until syrupy and coating the spoon. Strain, then off the heat whisk in the remaining 1 1/2 tablespoons (20 g) cold butter in small pieces. Adjust salt and pepper.
9. Let the Wellington rest on a rack for 10 minutes, uncovered so the pastry stays crisp. During the rest, the internal temperature climbs to 125 to 130°F (52 to 54°C), perfect medium-rare.
10. Slice with a serrated bread knife into 1 1/4 inch (3 cm) slices, sawing gently without pressing so you don't crush the pastry. Serve right away with the red wine sauce on the side.