Beef Wellington

Ingredients

• 55g pancetta or bacon, finely chopped
• 30g unsalted butter
• 340g mushrooms, preferably mixed cremini, white, shiitake, chanterelle or oyster mushrooms; very finely chopped
• 1 shallot, diced
• 2 garlic cloves, minced
• 2g fresh thyme leaves
• 15ml dry sherry or dry vermouth
• 1.4kg center-cut beef tenderloin
• 30ml extra-virgin olive oil, plus more for drizzling
• Kosher salt and black pepper
• 30ml Dijon mustard
• 10 to 12 thin slices prosciutto
• 1 large egg
• 450g puff pastry, thawed

Instructions

1. Using kitchen twine, tie the tenderloin into a 30 cm log, folding the thinner end onto itself. Use your hands to squeeze the meat firmly into shape.
2. Place pancetta in a cold 30 cm skillet. Cook over medium heat, stirring occasionally, until pancetta starts to brown, 6 to 8 minutes.
3. Add butter, raise heat to high, and stir in mushrooms and shallot. Cook until the liquid released by the mushrooms has cooked off, 4 to 7 minutes. Reduce heat to medium and continue to cook until mushrooms are browned, stirring frequently, another 18 to 23 minutes. (Take your time here, you want a deep golden color for the best flavor.) Scrape bottom of the skillet as necessary to prevent burning.
4. If the pan looks dry, drizzle in a little olive oil, then stir in garlic and thyme leaves. Cook until fragrant, another 1 to 2 minutes. Stir in sherry, scraping up the browned bits on the bottom of the pan. Scrape mixture into a medium bowl to cool. (Do not add salt at this point.)
5. In the same skillet, heat 30 ml olive oil over medium-high. Season beef generously with salt and pepper, then sear on all sides until browned, 1 to 2 minutes per side. Transfer to a plate and cool slightly. Remove any twine. Brush the meat all over with mustard.
6. On a clean work surface, overlap long sheets of plastic wrap to make a square about 38 cm wide. Place prosciutto slices on top to make a rectangle about 35 by 18 cm, arranging them in an even layer and overlapping the pieces slightly. Spread the cooled mushroom mixture on top.
7. Place beef along one long end of the prosciutto slices, and roll prosciutto tightly around beef. Wrap tightly with plastic wrap, twisting both ends like a candy wrapper. Chill in the refrigerator for at least 30 minutes and up to overnight.
8. Meanwhile, heat the oven to 205 °C and line a rimmed baking sheet with parchment paper. In a small bowl, whisk together the egg and 5 ml water. Lay the puff pastry on the prepared baking sheet, lightly draping it over the edges. The pastry needs to be at least 36 cm long and 33 cm wide to cover the beef; roll it out if needed.
9. Carefully unwrap and place chilled log along the edge of one long side of puff pastry. Roll beef up tightly, then place it seam-side down on the baking sheet. Tuck puff pastry over the ends of the beef to cover them, pinching to seal and folding underneath. Brush top and sides of pastry with egg wash, and use a small sharp knife to cut a few slits into the top of the pastry.
10. Bake until a thermometer inserted in the center reads 46 °C for rare, 25 to 35 minutes. This timing yields rare pieces at the thicker end and medium pieces at the thinner end of the loin. Remove from the oven and let rest for 10 minutes, then slice and serve warm.