Preheat your oven to 325.
Get out your most favorite 9 x 11 casserole baking dish - ideally one that is pretty enough to serve directly from.
In a large bowl, mix together cooked rice, onion, bell pepper, mushrooms, garlic, parsley, and cheese. Set aside.
In a medium bown, whish together egg, milk, oil, salt, pepper.
Pour the egg & milk mixture into the rice mixture. Carefully stir together until well incorporated.
Pour this into your casserole dish and spread out so it is even.
Bake for 20 minutes. Remove from the oven and increase the temperature to 350.
Evenly sprinkle the cornflakes on top of the casserole.
Bake for 5 minutes.
Remove from the oven and serve warm.