Cook rice. In a skillet, saute onion in 1 Tbsp butter for a few minutes. Add ground pork, water & seasonings; scramble-fry until cooked. Drain well & remove from skillet. Add another Tbsp of butter to skillet & saute drained mushrooms then blot on paper towel.
Grate cheese combo of choice. Preheat oven to 375 F. Line casserole baking dish with foil & butter.
Start layering with mushrooms, cheeses, rice, meat/onion combo & frozen green beans. Top with puff pastry. Cut a few slits in the pastry for vents. Brush with egg wash.
Bake for about 30-40 minutes or until pastry is golden. Remove from oven & allow to stand for about 15-20 minutes then invert on a serving plate. Remove foil paper & cut into serving pieces. If you wish, serve the casserole with a brown gravy.