To make the 6 egg whites from egg white powder, heat the water so it is warm (but not hot). Stir the powder into the water until just moistened.
Preheat and grease a large, oven-proof skillet on the stove over medium heat. Preheat the oven to 325-degrees.
Combine the egg whites (including the whites made from powder) in a large mixing bowl and beat them until frothy. Add the water and continue beating the egg whites until stiff (tips stand up straight).
In a separate bowl beat the 2 remaining egg yolks, the salt, and the white pepper. Fold the egg-yolk mixture into the egg whites until it develops a uniform color.
Spoon the egg mixture into the preheated skillet. Mound the eggs towards the edges, leaving a slight depression in the center. Cook the eggs for 6 minutes, without stirring.
Transfer the skillet into the oven and bake for 10-12 minutes, or until an inserted utensil comes out clean.
On a level surface, make a shallow cut slightly off-center in the omelette. Load your toppings (cheese and veggie burger) on the larger side of the cut. Fold the smaller side over, cut in half and serve immediately.