Mushroom stuffed brie en croute

Ingredients

• 1 wheel of Brie cheese
• 2 sheets of prepackaged pate brisee pastry
• 1 egg, beaten
• 1/2 lb mushrooms, finely chopped
• 1 small onion, minced
• 1/2 tsp ground nutmeg
• 1 tbsp Sherry or port
• 2 tbsp butter.