Lightly grease a 9 inch / 23 cm pie plate with nonstick spray. Lightly grease the outside of a dry measuring cup with nonstick spray. Preheat the oven to 375°F/190°C with an oven rack in the lower third of the oven.
In a medium bowl, toss the cooled cooked grains, parmesan (or other hard cheese), salt and pepper until well combined.
Add the egg white and mix until the mixture is evenly combined.
Spoon the grain mixture into the center of the prepared pan, and use the bottom of a greased measuring cup to press it evenly into the base and up the sides of the pan, aiming for full, even coverage all over the pan.
Transfer the pie pan to the oven and bake until the crust is set and starts very lightly browning around the outside edge, 12-15 minutes.
Cool completely before filling and baking again.
