Chicken Wellington - Puff Pastry

Ingredients

• 1 egg
• 1 tablespoon water
• 1 1/4 pound skinless, boneless chicken breast halves(4 breast halves)
• 1/2 teaspoon dried thyme, crushed
• 1/7 teaspoon black pepper
• 2 tablespoons butter
• 2 1/4 ounces sliced mushrooms, (about 3/4 cup)
• 1 medium onion, finely chopped (about 1/2 cup)
• 1 tablespoon chopped fresh parsley
• 1/3 of an 8-ounce package cream cheese, softened
• 1 tablespoon Dijon-style mustard or all-purpose flour
• 1/2 of a 17.3-ounce package Pepperidge Farm® Puff Pastry Sheets(1 sheet), thawed