In a large bowl, stir together all of the ingredients (except for the water) until well-combined. Pour into a greased 7-inch round soufflé dish or tall cake pan. Spray a piece of foil with cooking spray and cover the dish tightly with the foil, greased side down.
Set a wire rack or trivet inside of the inner bowl of an 8-quart or larger Instant Pot. Pour in the water and then place the casserole dish inside on top of the rack. Lock the lid and make sure the valve is set to seal. Pressure cook on high for 40 minutes. Allow to naturally release for 10 minutes before manually releasing any residual steam inside.
Carefully unlock the lid and lift up the casserole dish. Remove the foil and serve the casserole immediately.
Tip: If you want a golden brown top, you can place the casserole under the broiler until golden brown.