1. Prepare the Beef Fillet

• Season the beef fillet with salt and pepper on all sides.
• Sear the fillet in a hot pan with olive oil until browned. This seals in the flavor and moisture.
• Once browned, remove from heat and brush with mustard. Set aside to cool.

2. Make the Mushroom Duxelles

• Finely chop the mushrooms and sauté them over medium heat until they release and evaporate their moisture, creating a thick, spreadable paste.
• Remove from heat and allow to cool.

3. Assemble the Beef Wellington

• Lay out the prosciutto slices on a piece of plastic wrap, overlapping slightly to form a solid layer.
• Spread the mushroom duxelles evenly over the prosciutto.
• Place the seasoned beef fillet on top of the mushroom layer.
• Using the plastic wrap, roll the prosciutto and mushroom layer around the beef, securing it tightly. Chill for 10–15 minutes.

4. Encase in Puff Pastry

• Roll out the puff pastry to a size that will fully encase the wrapped beef fillet.
• Remove the plastic wrap from the beef, place it on the puff pastry, and wrap the pastry around the beef, sealing the edges.
• Brush the pastry with egg wash to create a glossy, golden crust when baked.

5. Bake the Beef Wellington

• Preheat the oven to 400°F (200°C).
• Place the wrapped beef on a baking sheet and bake for 30–35 minutes, or until the pastry is golden and crispy, and the beef reaches an internal temperature of 125°F for medium-rare.
• Allow the Beef Wellington to rest for 10 minutes before slicing.