1Spray 13x9-inch (3-quart) glass baking dish with cooking spray. Arrange potatoes in dish.
2Split whole chiles; lay flat over potatoes. Sprinkle with cheese.
3In large bowl with wire whisk, beat eggs, egg whites, milk, flour and garlic salt until well blended. Pour over mixture in dish. Cover with plastic wrap and refrigerate at least 4 hours or overnight.
4Heat oven to 350°F. Bake uncovered 45 minutes or until knife inserted in center comes out clean. Let stand 10 minutes before serving. Serve with salsa and sour cream.