Creating This Buffalo Chicken Casserole is straightforward. Here’s how to do it step-by-step:

1. Preheat the Oven: Preheat your oven to 350°F (175°C).
2. Grease the Baking Dish: Lightly coat a 9×13-inch baking dish with cooking spray or oil.
3. Mix Chicken and Sauce: In a large bowl, combine the shredded chicken, Buffalo sauce, and ranch dressing. Mix well until the chicken is evenly coated.
4. Add Pasta: Stir in the cooked pasta until fully incorporated.
5. Combine Cheeses and Onions: Add half of the shredded cheddar cheese, half of the mozzarella cheese, and half of the chopped green onions to the mixture. Stir until combined.
6. Transfer to Baking Dish: Pour the chicken mixture into the greased baking dish, spreading it evenly.
7. Top with Remaining Cheese: Sprinkle the remaining cheddar and mozzarella cheese over the top of the casserole for a cheesy finish.
8. Add Tortilla Chips: If using, sprinkle the crushed tortilla chips over the cheese layer for added crunch.
9. Bake: Place the casserole in the preheated oven and bake for 40-50 minutes or until the cheese is bubbly and the edges are slightly golden.
10. Cooling Time: Once done, remove from the oven and allow it to cool for about 15 minutes to set.
11. Garnish: Just before serving, sprinkle the remaining chopped green onions on top for freshness.

These steps will guide you to create an incredible Buffalo Chicken Casserole that is sure to be a hit.