Pre-heat oven to 400 if baking same day.
Mix cream cheese, soup, and water.
Add the broccoli, mushrooms and cheese.
Spoon into shallow 2 1/2 to 3 quart oval or rectangular baking dish.
Roll pastry on lightly floured surface to fit baking dish. Cover dish completely with pastry, pinching to edges of dish. Pierce with knife several times to allow venting. Brush entire surface with whisked egg.
You can either refrigerate for up to 24 hours or bake now.
Place dish on a cookie sheet. Bake for 30 minutes or until crust is golden brown. Remove from oven and allow to rest for 5 minutes before serving.