Heat a few tablespoons of olive oil in a large pot or Dutch oven over medium heat. Add the onion, celery, and carrots. Cook for 5–7 minutes, stirring occasionally, until the vegetables begin to soften.
Stir in the minced garlic, Calabrian chilies, granulated garlic, and Italian seasoning. Cook for 1 minute.
Sprinkle the flour over the vegetables and stir continuously for 1–2 minutes.
Gradually pour in the chicken stock, stirring constantly to prevent lumps. Add the water, tomato passata, and rosemary sprig.
Bring to a gentle boil, then reduce the heat to medium-low. Cook for 20 minutes or until the vegetables are tender and the broth thickens a bit.
Stir in the uncooked orzo and cook uncovered for 10–12 minutes, stirring frequently to prevent it from sticking to the bottom of the pot.
Reduce the heat to low and stir in the shredded chicken and heavy cream. Simmer for another 2–3 minutes, or until the chicken is heated through. Remove the rosemary sprig and season with salt and pepper.
Serve immediately with freshly grated Parmesan cheese and chopped parsley, if desired and enjoy!