1. Preheat oven to 400°F.
2. Place butter in a 9-by-13-inch baking pan. Place pan in oven until butter is melted. Pour half the butter into a small bowl and set aside.
3. Beat eggs and egg whites lightly in a large bowl. Stir in flour, baking powder, chiles, all cheeses, salt, and pepper. Mix well.
4. Pour egg mixture into baking pan. Pour reserved butter evenly over the top.
5. Bake for 15 minutes. Reduce heat to 350°F and bake 35 to 40 minutes or until casserole is set.
1. You can make this dish in advance and reheat it, covered, in a 325°F oven until hot.
2. Spice things up with a dab of green chile enchilada sauce or your favorite salsa.
3. A tossed green salad is a great accompaniment for this casserole.
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