Gather all the ingredients and ensure your workspace is clean and organized.

Preheat your oven to 350°F (175°C).

In a large pot, bring salted water to a boil. Add the rotini pasta and cook according to package instructions until al dente, around 8-10 minutes. Drain and set aside.

In a skillet over medium heat, add the diced chicken, season with salt and pepper, and sauté for 5-7 minutes until warmed through.

In a medium saucepan, melt the butter over medium heat, add flour to create a roux, whisking for 1-2 minutes until golden.

Gradually whisk in the milk, cooking and whisking until thickened, about 3-5 minutes.

Lower the heat, add cream cheese, whisk until melted and combined.

Stir in sharp cheddar cheese and buffalo sauce until fully melted and creamy.

In a large mixing bowl, combine the drained pasta, cheese sauce, and sautéed chicken, stirring until coated.

Transfer to a greased baking dish, top with panko breadcrumbs, and drizzle melted butter over top if desired.

Bake in the preheated oven for about 20-25 minutes, until bubbly and golden brown.

Let cool for a few minutes, then sprinkle with sliced green onions before serving.