Heat olive oil in a large pot over medium heat.
Sauté the diced onion until translucent, about 3 minutes.
Add minced garlic and cook for an additional minute.
Stir in the diced carrot and celery, cooking until slightly softened.
Pour in the broth and bring to a boil.
Add the pastina pasta to the boiling broth.
Reduce heat and let simmer for 10 minutes or until pasta is al dente.
Season with salt and pepper to taste.
Remove from heat and stir in fresh parsley.
Serve hot, garnished with Parmesan if desired.