Cook turkey and onion in a nonstick skillet over medium-high heat until browned, stirring to crumble. Remove from heat; add cumin and next 5 ingredients (cumin through beans). Stir well; set aside.
Arrange half of green chiles in an 11 x 7-inch baking dish; top with 1/2 cup cheese. Spoon mounds of turkey mixture onto cheese; spread gently, leaving a 1/4-inch border around edge of dish. Top with corn. Arrange remaining green chiles over corn; top with 1/2 cup cheese.
Combine flour and salt in a bowl; gradually add milk, hot sauce, eggs and egg whites, stirring with a whisk until blended. Pour over casserole.
Bake at 350* for 1 hour and 5 minutes or until set; let stand 5 minutes. Garnish with onion slices and cilantro, if desired.