Preheat the oven to 190°C. Lightly coat a rectangular baking dish with nonstick cooking spray. Coarsely crush the chips by hand and spread half of them into the bottom of the baking dish.
Whisk the egg whites, eggs, milk, ancho powder, and pepper in a large bowl until well combined. Stir in the chopped chiles, chopped coriander, and half each of the Cheddar and pepper jack cheeses; pour into the pan. Sprinkle the remaining chips over the egg mixture. Bake until the casserole is set around the edges but a little loose in the center, 20 to 25 minutes.
Sprinkle with the remaining cheeses and continue to bake until the cheeses are melted and the casserole is set in the center, about 10 minutes. Let stand 10 minutes. Serve with the salsa and, sour cream, if using. Garnish with whole coriander leaves.