Dice the onion, carrot, and celery. Mince the garlic. Cut chicken breasts into small, bite-sized pieces.

Heat olive oil in a large pot over medium heat. Add chicken pieces and cook until browned and cooked through, about 8 minutes. Remove and set aside.

In the same pot, add more oil if needed. Sauté onion, carrot, and celery until vegetables are tender, about 5 minutes. Add garlic and cook for another minute.

Pour in chicken broth. Bring to a boil, then add macaroni. Reduce heat to simmer and cook until pasta is al dente, about 10 minutes.

Return cooked chicken to the pot. Season with salt and pepper to taste. Simmer for another 5 minutes to meld flavors.

Stir in chopped parsley if desired. Serve hot.