Ingredients
Equipment
Method
Prepare the oven
- Heat the oven to 400°F and line a 13x18-inch sheet pan with parchment paper.
Cook the beef
- Pat the tenderloin dry and season it all over with the kosher salt and black pepper.
- Heat the olive oil in a 12-inch skillet over medium-high heat until shimmering.
- Sear the tenderloin, turning it, for 2 to 3 minutes per side until browned all over.
- Transfer the beef to a plate and remove and discard the twine.
- Brush the beef all over with the Dijon mustard, then let it cool completely.
Make the duxelles
- Wipe out the skillet and melt the butter over medium heat.
- Add the mushrooms, shallot, thyme, and kosher salt; cook, stirring often, for 15 to 20 minutes until the mixture is dry and beginning to brown.
- Spread the mushroom mixture on a plate and let it cool completely.
Assemble and bake
- Lay a large sheet of plastic wrap on the counter and arrange the prosciutto slices on it, overlapping them to form a rectangle.
- Spread the cooled mushroom mixture over the prosciutto and set the beef in the center.
- Wrap the beef snugly and chill for 20 minutes.
- Lightly dust the counter with the flour and roll the puff pastry into a 12x14-inch rectangle.
- Unwrap the beef and place it in the center of the pastry.
- Beat the egg and water together in a small bowl.
- Brush the pastry edges with egg wash, fold the pastry around the beef, and press the seams to seal.
- Place the Wellington seam-side down on the prepared sheet pan.
- Use any pastry scraps to decorate the top and score the pastry lightly without cutting through.
- Brush the pastry with the remaining egg wash and chill for 15 minutes.
- Bake for 40 to 55 minutes until the pastry is deeply golden and a thermometer inserted through an end into the center of the beef reads 145°F.
- If the pastry browns before the beef reaches temperature, tent it loosely with foil.
- Rest the Wellington for 10 minutes before slicing.
Notes
For clean slices, let the Wellington rest for the full 10 minutes before cutting. Refrigerate leftovers for up to 3 days; freezing the baked Wellington is not recommended. For a gluten-free adaptation, use gluten-free puff pastry and flour.
