Heat olive oil in a large pot over medium heat. Add diced chicken and season with Cajun seasoning, salt, and pepper. Cook until browned and cooked through, about 5-7 minutes.
Remove chicken from the pot and set aside. In the same pot, sauté diced onions and garlic until softened and fragrant, about 2-3 minutes.
Add diced bell pepper if using and cook for an additional 2 minutes.
Stir in orzo pasta, chicken broth, and heavy cream. Bring the mixture to a boil.
Reduce heat to low and simmer for 10-12 minutes, stirring occasionally, until orzo is tender.
Return cooked chicken to the pot, stir in Parmesan cheese until creamy and well combined. Adjust seasoning if needed.
Serve warm, garnished with fresh parsley if desired.