Preheat oven to 350 degrees F. Coat a square baking dish with cooking spray and set aside. Heat olive oil in skillet over medium heat. Add green onions, cilantro and jalapeños (if using). Cook for 3 to 5 minutes, or until soft and fragrant.
Add the green mixture to a large bowl, along with tortilla pieces, chicken, tomatoes, 1 cup of the cheese, enchilada sauce, lime juice, salt and pepper. Pour mixture into prepared baking dish and top with the remainder of the cheese.
Bake in the preheated oven for 25 minutes, or until heated through. Top with sour cream, avocados, crushed tortilla chips or extra enchilada sauce, if desired.