Warm the olive oil in a large pot over medium heat until shimmering. Add the diced chicken and season with Cajun seasoning, salt, and pepper. Cook for 5 to 7 minutes, stirring occasionally, until golden brown and cooked through with no pink remaining.

Remove the chicken and set aside on a plate. Leave the browned bits in the pot for added flavor.

In the same pot over medium heat, add the diced onion and minced garlic. Cook for 2 to 3 minutes until soft and fragrant. Stir in the diced bell pepper if using and cook for one more minute.

Pour in the orzo, chicken broth, and heavy cream. Stir to combine and bring to a gentle boil.

Reduce heat to low and cover the pot. Simmer for 10 to 12 minutes, stirring every few minutes to prevent sticking, until the orzo is tender and has absorbed most of the liquid. Add a splash of broth if it thickens too quickly before the orzo is done.

Stir the cooked chicken and grated Parmesan into the pot. Mix until the cheese melts completely and the sauce is creamy and smooth. Taste and adjust seasoning as needed.

Ladle into bowls and garnish with fresh parsley before serving.