Bring a large pot of salted water to a boil. Cook the pasta al dente, according to package directions. Drain.In the same pot set over medium-high heat, add 2 tablespoons olive oil, the onion, chicken, and 1 tablespoon cajun seasoning. Cook until browned all over, about 5 minutes. Spoon the chicken onto a plate.To the pot, add 2 tablespoons olive oil, the bell peppers, and garlic. Cook another 5 minutes until the peppers are soft. Stir in 1-2 teaspoons cajun seasoning. Add a pinch each of red pepper flakes, salt, and pepper. Cook another minute, until the spices are fragrant, then pour in the broth and milk. Add the cream cheese. Whisk until smooth. Bring the sauce to a gentle simmer and cook 5 minutes, until thickened slightly.Stir in the parmesan. Then toss in the pasta and chicken and cook 2-3 minutes. Remove from the heat and stir in the basil. Serve immediately topped with additional basil. Enjoy!