Heat olive oil and butter in a large skillet over medium heat.
Add the diced chicken, season with salt and pepper, and cook until golden and cooked through.
Remove chicken and set aside. In the same skillet, add garlic and onion. Sauté until fragrant.
Stir in orzo and toast lightly for 1–2 minutes.
Pour in chicken broth and bring to a boil. Reduce heat, cover, and let it simmer for about 10 minutes.
Add the cooked chicken back in, then stir in heavy cream and Parmesan until everything's creamy and delicious.
Toss in spinach (if using) and let it wilt.
Top with chopped parsley and serve hot.