Prepare the Soffritto: In a large pot, heat the olive oil over medium heat. Add the diced onion, carrots, and celery. Sauté for 5-7 minutes until the vegetables begin to soften and the onion becomes translucent.
Build the Flavor Base: Add the minced garlic and cook for another minute until fragrant. Season with a pinch of salt and pepper.
Add the Broth: Pour in the chicken broth and add the Parmesan rind if using. Bring to a gentle boil.
Cook the Pastina: Once boiling, add the pastina to the soup. Reduce heat to medium-low and simmer for about 8-10 minutes, or until the pasta is tender. Stir occasionally to prevent the tiny pasta from sticking to the bottom.
Final Touches: Taste and adjust seasoning with salt and pepper. Remove the Parmesan rind.
Serve: Ladle the hot soup into bowls. Garnish with fresh parsley and offer grated Parmesan cheese at the table.