Beef Wellington

Preheat oven to 400°F (200°C) for convection or 425°F (220°C) for regular. Trim any excess fat from the beef tenderloin. Season generously with salt and pepper. Heat 2 tablespoons of olive oil in a cast iron skillet over medium-high heat until shimmering. Sear the tenderloin on all sides until deeply browned, about 1-2 minutes per side. The center should remain rare. Remove from skillet and let cool slightly.

While the beef is still warm, brush it all over with Dijon mustard. This helps the duxelles adhere and adds flavor.

Finely chop the mushrooms, shallots, and garlic. A food processor can be used, but be careful not to over-process into a paste. Aim for a coarse, crumbly texture.

Heat 2 tablespoons of olive oil in a large skillet over medium heat. Add the chopped shallots and garlic and sauté until softened and translucent, about 3-5 minutes. Add the chopped mushrooms and fresh thyme sprigs. Season with salt. Cook, stirring occasionally, until the mushrooms have released their liquid and it has evaporated, and the mixture is dry and paste-like, about 10-15 minutes. This drying process is crucial to prevent a soggy bottom.

Pour in the whiskey and scrape up any browned bits from the bottom of the pan. Let it simmer and reduce until almost completely evaporated. Remove the thyme sprigs. Let the duxelles cool slightly.

Lay out a large piece of plastic wrap on a clean surface. Arrange 6-7 slices of prosciutto on the plastic wrap, overlapping them slightly to form a rectangle large enough to encase the beef. Spread the cooled mushroom duxelles evenly over the prosciutto. Place the mustard-coated beef tenderloin on top of the duxelles.

Using the plastic wrap to help, carefully wrap the prosciutto and duxelles tightly around the beef tenderloin, forming a neat log. Twist the ends of the plastic wrap to secure and create tension, ensuring a compact shape. Chill in the refrigerator for at least 30 minutes (or up to 24 hours) to firm up.

Lightly flour a clean surface and roll out the puff pastry sheet to about 1/8 inch (3mm) thickness. Brush the pastry with egg wash. Unwrap the chilled beef log and place it on the puff pastry, seam-side down. Trim any excess pastry, leaving enough to fully enclose the beef. Fold the pastry over the beef, sealing the edges tightly. Trim any excess pastry and pinch the seams closed. Place seam-side down on a baking sheet lined with parchment paper.

Using a lattice cutter or a sharp knife, score a decorative pattern on the top of the puff pastry. Brush the entire surface with egg wash. Sprinkle generously with flaky sea salt.

Bake in the preheated oven for 20-25 minutes for medium-rare (internal temperature of 125-130°F / 52-54°C), or longer for more well-done. The pastry should be golden brown and puffed.

Remove from oven and let rest for at least 10 minutes before slicing. This allows the juices to redistribute. Slice into thick portions and serve immediately.