1. Prepare the Beef Tenderloin

Start by trimming the beef tenderloin to remove any silver skin or excess fat. Using a sharp knife, carefully trim the meat, ensuring it remains in a uniform shape.

Season the beef generously with salt and freshly ground black pepper. In a large skillet, heat the olive oil over medium-high heat. Once hot, sear the beef on all sides until it is nicely browned (about 2-3 minutes per side). This step helps to lock in the juices and adds a layer of rich flavor to the meat.

Once seared, remove the beef from the skillet and let it cool slightly. Afterward, brush the entire surface of the beef with Dijon mustard. The mustard adds flavor and helps the mushroom mixture stick to the meat during assembly.

2. Prepare the Mushroom Duxelles

The mushroom duxelles is a key element of Beef Wellington, providing a deep umami flavor and moisture to balance the beef and pastry.

To begin, finely chop the mushrooms. You can use cremini, button mushrooms, or a mixture of both. In a medium skillet, melt the butter over medium heat. Add the chopped shallots and garlic and sauté for about 2 minutes, until softened and fragrant.

Next, add the chopped mushrooms to the pan and cook them down, stirring frequently. The mushrooms will release a lot of moisture, so continue cooking until the liquid evaporates and the mushrooms become tender and browned (about 10-12 minutes). If you’re using wine, pour it in after the mushrooms have browned and let it cook off for another 2-3 minutes.

Season the duxelles with salt, pepper, and fresh thyme leaves. Once the mixture is cooked, remove it from the heat and set it aside to cool completely.

3. Assemble the Wellington

Once the beef and duxelles have cooled, you can begin assembling the Wellington.

Lay out a large piece of plastic wrap on a flat surface. Arrange the prosciutto slices in a single layer, slightly overlapping. Spread the mushroom duxelles evenly over the prosciutto, making sure it covers the entire surface.

Carefully place the mustard-coated beef in the center of the mushroom-covered prosciutto. Using the plastic wrap, gently roll the beef, ensuring the prosciutto and mushrooms fully encase the meat. Once rolled, wrap the entire bundle tightly in plastic wrap and refrigerate for at least 30 minutes. Chilling the beef helps it hold its shape during the wrapping process.

4. Wrap in Puff Pastry

While the beef is chilling, roll out the puff pastry on a lightly floured surface. If using store-bought puff pastry, ensure it is thawed and ready to work with.

Unwrap the chilled beef from the plastic wrap and place it on the center of the pastry. Fold the pastry around the beef, trimming any excess pastry at the ends. Seal the edges well and fold them under the beef to create a neat package. Use a fork to press down the edges to seal them securely.

Once the Wellington is fully wrapped, brush the entire surface with the beaten egg to create a glossy, golden crust. At this point, you can also score the top of the pastry lightly with a knife to create a decorative pattern if desired.

5. Bake the Beef Wellington

Preheat the oven to 400°F (200°C). Place the wrapped Beef Wellington on a baking sheet lined with parchment paper, seam side down.

Bake for 45-50 minutes, or until the pastry is golden brown and crisp. The internal temperature of the beef should reach 120°F (49°C) for medium-rare, or adjust according to your preferred doneness.

Once the Wellington is baked, remove it from the oven and let it rest for about 10 minutes before slicing. This allows the juices to redistribute, ensuring the beef remains tender and juicy.

6. Serve and Garnish

After the resting period, slice the Beef Wellington into generous portions. Serve each slice with a garnish of fresh parsley for a touch of color. The Wellington can be served as a stand-alone dish or accompanied by a variety of sides such as roasted vegetables, mashed potatoes, or a crisp salad.