In a large pot or Dutch oven, heat the olive oil over medium-high heat. Add the chicken pieces and season with salt and pepper. Cook until browned on all sides, about 5-7 minutes. Remove the chicken from the pot and set aside.

In the same pot, add the diced onion and sauté for about 3-4 minutes until softened. Stir in the minced garlic and cook for an additional 1 minute until fragrant.

Add the cherry tomatoes, oregano, basil, and red pepper flakes (if using) to the pot. Cook for another 2-3 minutes until the tomatoes start to soften.

Stir in the orzo pasta and pour in the chicken broth. Bring the mixture to a boil, then reduce the heat to a simmer. Return the chicken to the pot and cover. Cook for about 10-12 minutes, or until the orzo is tender and has absorbed most of the liquid.

Once cooked, stir in the chopped spinach and grated Parmesan cheese. Cook for an additional 2 minutes until the spinach wilts.

Serve hot, garnished with fresh basil leaves.