Preheat oven to 400°F. While heating, set the beef tenderloin out to come to room temperature. Season generously with salt and pepper on all sides.
2 6 ounce Beef tenderloin, Salt and pepper to taste
Heat a cast iron skillet over high heat. Add a drizzle of olive oil, pat the beef dry, then sear for 2 minutes per side until browned.
Olive oil for searing
Remove beef from the heat and let it rest. In the same skillet, melt butter over medium heat. Once melted, add finely diced shallots and garlic. Saute until translucent, about 3 minutes.
1 Shallot, 1 Tablespoon Butter, 1 clove Garlic
Add mushrooms, salt, and pepper, then cook until the mushrooms release their liquid and it evaporates.
½ cup Mushrooms, Salt and pepper to taste
Stir in parsley and cook for 1 minute longer, then remove from the heat and allow to cool.
1 Tablespoon Parsley
Assembling Beef Wellington in Puff Pastry
Once the beef and mushrooms have cooled completely, take a large piece of plastic wrap and lay the prosciutto on top of it. Spread Dijon mustard evenly over top.
2 Tablespoons Dijon mustard, 2 slices Prosciutto
Place cooled beef tenderloin on top of the prosciutto. Then, spread a thin layer of the mushroom mixture over the top.
Mushroom Duxelles
Using the plastic wrap, wrap the beef tenderloin tightly with the prosciutto and duxelles, and repeat the process with the second layer of beef.
Roll out the puff pastry dough on a lightly floured surface. Cut it into squares, or rectangles, large enough to wrap around each portion of beef.
½ package Puff pastry
Create an egg wash by beating an egg with a little water. Remove plastic, then wrap each piece of beef in puff pastry. Brush the egg wash around the edges to help it seal. Finally, place the beef wellingtons on a lined baking sheet, seam side down.
1 Egg
Brush the pastry with egg wash, coating all of it well.
Bake for 20-25 minutes, or until the pastry is golden brown and crisp and the beef reads 135°F internally using a meat thermometer. Remove from the oven, let rest, then slice and serve with espagnole sauce!
Notes
Be careful not to overcook the meat. Remove it from the oven as soon as the internal temperature reaches 135°F or just below, then let it rest for 10 minutes before slicing.
Make sure to cook all of the moisture out of the mushroom duxelles, and keep the layer of mushrooms thin. If it's too thick or there's too much liquid, it will make the puff pastry soggy.
Do not skip the prosciutto layer - this guards the beef from releasing too many juices into the rest of the layers.
Don't skip searing the meat. This is an important step for cooking a juicy, tender beef wellington.
Always let the ingredients cool first. You must let the mushroom duxelles and beef tenderloin cool before wrapping them in puff pastry, or it will ruin the texture of the beef wellington.