Mushroom Pie

Ingredients:

• dough rolled out for top & bottom pie crust, refrigerated for 1 hour
• 2 pounds (900 gr) mushrooms
• 3 tablespoons butter
• 1 cup (¼ liter) sliced onions
• salt
• pepper
• ½ teaspoon Worcestershire sauce
• 1 tablespoon lemon juice
• ¼ cup (4 tablespoons, 60 ml) sherry
• 1 pound (450 gr) "swiss cheese" (Gruyere or Emmenthaler)
• 1 beaten egg white

Instructions: