Directions:

Preheat oven to 425 F. Coat a large rimmed baking sheet with nonstick spray.

In a medium nonstick skillet, cook mushrooms, garlic and 1/4 teaspoon of the thyme over medium heat 6 to 8 minutes. Remove skillet from heat and chill.

Unfold puff pastry sheets and cut each crosswise in half. Spoon the chilled mushroom mixture onto the center of the 4 pieces of puff pastry. Season both sides of the meat with salt and pepper and place them on top of the mushroom mixture. Bring the corners and edges together to seal completely. Place seam side down on baking sheet. Cut 2 - 3 slits in the pastry case to vent steam.

Bake until pastry is golden, 20 to 25 minutes depending on desired doneness. Use an instant-read thermometer to check meat:
Rare: 120 - 130 degrees
Medium-Rare: 130 - 135 degrees

Cover pastry with aluminum foil if it gets too brown during cooking.

Meanwhile in skillet, combine the remaining 1/4 teaspoon thyme, gravy, wine and tarragon. Bring to a boil. Let meat rest on a cutting board 10 minutes before slicing. Serve Beef Wellington with wine sauce.