Preheat the oven to 375°F (190°C).
Cook the penne pasta according to package instructions until al dente. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Season the chicken breasts with Cajun seasoning, garlic powder, onion powder, salt, and pepper. Add the chicken to the skillet and cook for about 5-7 minutes per side, or until fully cooked. Remove from the skillet, let rest for a few minutes, and then dice into bite-sized pieces.
In a mixing bowl, combine the softened cream cheese, chicken broth, and sour cream. Mix until smooth.
Add the cooked pasta and diced chicken to the mixing bowl and stir until everything is well coated with the creamy mixture.
Transfer the mixture into a greased 9x13 inch baking dish. Sprinkle the shredded mozzarella cheese evenly over the top.
Bake in the preheated oven for 25-30 minutes, or until the cheese is bubbly and golden.
Remove from the oven and allow to cool for a few minutes. Garnish with chopped green onions before serving.