Chile relleno casserole

This recipe comes from one of my PhD committee members, Linda. Thanks to the CSA, I again had a whole bunch of chiles, Anaheims I believe. I often get chiles rellenos when I eat at Mexican restaurants. They're so good. I always figured they were somewhat of a production to make, until Linda told me about her short cut way. The amounts here are definitely guesses, I should have jotted them down as I was making it (this is a common theme lately), so if it looks like too much or too little, definitely adjust! The key to the recipe is the batter; whipping the egg whites makes it light and crispy, mimicking the results of frying batter-dipped chiles.

Ingredients
1 lb potatoes, diced
1 onion, diced
salt & pepper
~at least 1 dozen green chiles: Anaheim, poblanos, hatch most types would work
~1/2 lb of cheese, preferably Cabot Hunter's X-sharp, sliced or grated.
optional green chile
some butter
2 eggs
~1/3 cup flour
1/2 t baking powder
1/2 t salt
1/2 t pepper

1. Preheat oven to 375.
2. Sautee potatoes and onions in butter till potatoes are done, season with S&P to taste.
3. Roast chiles the same way as directed in the green chile recipe. Linda says you can skip this step if you don't have time - or use canned roasted chiles.
4. Butter a medium-sized casserole or baking pan.
5. Layer half the green chiles, the potato and onion mixutre, the cheese, and top with the other half of the green chiles or the optional green chile. If your chile are still whole, you can make it fancier by stuffing them instead of layering.
6. Separate the eggs, reserving yolks and transferring whites to a mixing bowl.
7. Beat egg whites with an electric mixer till the soft peak stage.
8. Lightly beat yolks in a separate small bowl.
9. Very lightly fold in the yolks, flour, baking powder and S&P. The batter should be light and thinner than pancake batter.
10. Pour the batter evenly over the casserole.
11. Bake for about 40 minutes, till the batter is completely cooked in the middle.

Serve with warm corn tortillas, chopped cilantro, plain yogurt or sour cream, and salsa (fresh, if available!), and/or rice and black beans.