Add the chicken breasts to the pot. Pour in the chicken broth, Buffalo sauce, and ranch dressing.
Add the cubed cream cheese. Cover and cook until the chicken is tender and fully cooked through.
Remove the chicken from the sauce and shred or chop it into bite-size pieces.
Stir the uncooked penne into the creamy Buffalo sauce. Cook until the pasta is tender, stirring occasionally so it does not stick.
Add the cooked chicken back to the pot and stir to combine.
Stir in the shredded mozzarella and cheddar cheese blend until melted and creamy.
Add 1/2 cup chopped green onions and mix gently.
Serve warm with the remaining 2 tablespoons chopped green onions sprinkled over the top.