Bring a large pot of salted water to a boil. Add rotini pasta and cook until al dente. Drain and set aside.
In a skillet, cook diced chicken with salt and pepper until golden and fully cooked (about 5–7 minutes). Set aside.
In a saucepan, melt butter over medium heat. Whisk in flour to form a roux. Slowly add milk, whisking until smooth. Stir in cream cheese until melted. Add cheddar cheese and buffalo sauce, mixing until creamy.
In a large mixing bowl, toss cooked pasta, chicken, and cheese sauce until well coated.
Transfer mixture into a greased baking dish. Sprinkle panko breadcrumbs evenly over the top.
Preheat oven to 350°F (175°C). Bake for 20–25 minutes or until bubbly and golden brown.
Garnish with sliced green onions and serve hot.
