Heat the olive oil or butter in a large deep skillet or Dutch oven over medium heat. Add the cooked shredded chicken, garlic powder, salt, and black pepper. Cook for 2–3 minutes, stirring occasionally, until the chicken is heated through and lightly seasoned. Transfer the chicken to a plate and set aside.
Pour the chicken broth, heavy cream, and buffalo wing sauce into the same pot, stirring to combine. Add the uncooked rotini pasta and stir well. Bring the mixture to a gentle boil, then reduce the heat to low. Simmer uncovered for 10–12 minutes, stirring occasionally, until the pasta is tender and most of the liquid has been absorbed.
Add the softened cream cheese, shredded Parmesan cheese, and shredded mozzarella cheese. Stir until all of the cheese has melted into a smooth, creamy sauce.
Return the cooked chicken to the pot and stir until everything is evenly coated in the buffalo cheese sauce. Taste and adjust with additional salt, pepper, or buffalo sauce if desired.
Spoon the buffalo chicken pasta into bowls and garnish with sliced green onions or chopped parsley, if desired. Serve hot and enjoy!