Warm the olive oil in a large pot or Dutch oven over medium heat. Introduce the chopped onion, carrots, and celery. Cook, stirring occasionally, until the vegetables have softened, about 8-10 minutes.
Stir the minced garlic and grated ginger into the pot. Continue cooking for another minute until aromatic.
Place the chicken pieces into the pot and sprinkle with a pinch of salt and pepper. Cook, stirring, until the chicken is lightly browned on all sides, about 3-5 minutes.
Add the chicken broth and water. Incorporate the dried oregano, thyme, and red pepper flakes (if using). Bring to a simmer, then lower heat to low, cover, and cook for at least 20 minutes.
Add the small pasta. Raise heat to medium and cook according to package directions until al dente.
Mix in lemon juice, beginning with half a lemon. Taste and add more if desired.
Adjust seasoning with salt and pepper.
Ladle into bowls, garnish with parsley and Parmesan if using.