Beef Wellington - Pepperidge Farm

Ingredients

• 2.5 pounds center cut beef tenderloin
• 1/2 teaspoon ground black pepper (optional)
• 1 egg
• 1 tablespoon water
• 1 tablespoon butter
• 2 cups finely chopped mushrooms
• 1 medium onion, finely chopped (about 1/2 cup)
• 2 tablespoons all-purpose flour
• 1/2 of a 17.3-ounce package Pepperidge Farm® Puff Pastry Sheets (1 sheet), thawed