Spray a 13x9 pan with cooking spray.
Add green chiles to the pan.
Spread the cheese evenly over the green chiles.
In a medium bowl, whisk together the milk and flour.
Add eggs, evaporated milk, salt and pepper.
Stir ingredients together until well-combined and pour mixture over cheese layer.
Bake uncovered at 350 degrees for 40 minutes.
Remove pan from oven and spread the salsa evenly over the top.
Return pan to oven and cook an additional 15 minutes.
Check the center of the casserole to make sure ingredients are set. Sides will be puffed with the center slightly lower. If center is not set, cook for additional 6-8 minutes.
Garnish with chopped cilantro and green onions if desired.