- 4 Tbsp olive oil, divided
- Salt and freshly ground pepper
- 1 1/2 lb beef tenderloin
- 1/2 lb cremini mushrooms, chopped
- 1/4 shiitake mushrooms, stems removed and chopped
- 1 shallot, chopped
- 1/4 cup dry sherry
- 1 Tbsp soy sauce
- 1 tsp chopped fresh thyme
- 1 sheet puff pastry, thawed
- 3 Tbsp Dijon or coarse grain mustard
- 1 egg, lightly beaten with 1 tsp water
Preheat oven to 400°. Line a rimmed baking sheet with parchment paper or a silicone mat.
In a 3 1/2-quart wide Dutch oven over medium-high heat, warm 2 tablespoons olive oil. Season beef liberally with salt and pepper. Sear all sides of the beef until browned. Transfer to a plate.
Add remaining 2 tablespoons olive oil. Add mushrooms and shallot and cook, stirring occasionally, until tender and all moisture has cooked out, about 8 minutes. Add sherry, soy sauce, and thyme, season with salt and pepper, and cook for 3 minutes until evaporated. Transfer to a plate and let cool.
Place puff pastry sheet on prepared baking sheet. Roll out to extend 1 more inch. Slather dough with mustard and evenly spread mushroom-shallot mixture over mustard, leaving ½” border around dough. Place beef in center of pastry dough and bring bottom portion of dough up and over beef. Repeat with top portion of dough, covering up beef. Turn over entire pastry wrapped dough, seam side down on baking sheet.
Dock dough in several places with a fork or scissors. Using a pastry brush, brush egg wash over pastry. Bake until pastry is puffed and golden brown and beef reaches an internal temperature of 125° for medium-rare with an instant read thermometer, 20-25 minutes. Let rest for 10 minutes before serving.