Preheat the oven to 375 degrees Fahrenheit and spray a 9X13 baking pan with a non-stick cooking spray.
Cook 12 ounces penne pasta according to the package directions until al dente. Drain, rinse, and set aside.
In a large mixing bowl, combine 8 ounces softened cream cheese, 2 tablespoons ranch seasoning mix, ? cup milk, and ¼ cup buffalo sauce. Stir until smooth and well combined.
Add 3 cups cooked shredded chicken, the cooked penne pasta, ½ cup shredded Monterey Jack cheese, and ½ cup shredded cheddar cheese. Stir until evenly coated.
Pour the mixture into the baking dish. Drizzle the remaining ¼ cup buffalo sauce over the top. Sprinkle the remaining ½ cup shredded Monterey Jack cheese and ½ cup shredded cheddar cheese over the casserole.
Bake for 25-30 minutes until heated through and the cheese on top is fully melted.
Remove from the oven, let it rest for 10-15 minutes and top with the sliced green onions. Then it’s ready to serve and enjoy!
Notes
Refrigerate the leftovers in an airtight container for up to 5 days.