In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté until translucent, about 5 minutes. Stir in the minced garlic and cook for an additional minute until fragrant.

Add the sliced carrots and diced celery to the pot. Cook for about 5 minutes, stirring occasionally, until the vegetables begin to soften.

Add the cubed chicken breasts to the pot and cook until they are no longer pink, about 5-7 minutes.

Pour in the chicken broth and bring the mixture to a boil. Reduce the heat to a simmer and add the frozen peas, thyme, rosemary, salt, and pepper. Simmer for 15 minutes.

In a small bowl, whisk together the heavy cream and flour until smooth. Slowly pour this mixture into the soup, stirring constantly to avoid lumps. Cook for an additional 5 minutes, or until the soup thickens slightly.

Taste and adjust seasoning if necessary. Serve hot, garnished with fresh parsley.