Preheat the oven to 400 degrees.
In a bowl, mix together
10 ounces part-skim mozarella cheese with 3.5 ounces cooked, shredded chicken, 1/2 tsp garlic powder and 1/2 tsp onion powder. Set aside.
Whip the egg whites on high with 1/2 tsp of cream of tartar, 1/2 tsp garlic powder and 1/2 tsp onion powder until stiff peaks form. This took about five-ish minutes for my Kitchenaid stand mixer.
Spray a 9 x 13 glass baking dish with cooking spray. Spread half of the whipped egg whites on the bottom of the pan.
Carefully remove the canned chiles, split down one side and place a tablespoon or two (depending on the size of the chile) onto the opened chile. Fold the chile around the filling and press the filled chile into the mixture, lining them up like you would an enchilada. Make sure to press the chile into the eggs so the eggs envelop the sides of the chile. Repeat the process for the remaining 11 chiles, lining them up like you would if you were making enchiladas.
Spread the remaining whipped egg whites over the chiles and sprinkle with the remaining cheese.
Cover with foil and bake 30 minutes. Remove from oven, increase the temperature to 450 degrees, remove foil and return to the oven for another ten-ish minutes until the cheese on top is bubbly and the eggs are browned a bit. (See above picture).
This is best served fresh from the oven (let it sit a few minutes to let the cheese settle before serving). However, reheated leftovers are amazing too.
Servings: 4 (3 chile rellenos = 1 serving)