Prepare the Vegetables
Dice the onion, carrot, and celery into small pieces. Mince the garlic and set everything aside.
Sauté the Aromatics
Melt the butter in a large pot over medium heat. Add the onion, carrot, and celery. Cook for 5–7 minutes, stirring occasionally, until softened. Add the minced garlic and cook for another minute.
Add the Broth
Pour the chicken broth into the pot and bring it to a gentle boil. Season with salt and pepper to taste.
Cook the Pasta
Add the pastina to the boiling broth. Reduce the heat to medium-low and simmer for 6–8 minutes, stirring occasionally, until the pasta is tender.
Prepare the Egg Mixture
In a small bowl, whisk the eggs and Parmesan cheese together until smooth.
Incorporate the Egg Mixture
Slowly drizzle the egg mixture into the pot while stirring continuously to create delicate strands of egg throughout the soup.
Garnish and Serve
Stir in the fresh parsley and adjust the seasoning if needed. Ladle the soup into bowls and serve hot. Optionally, top with extra Parmesan cheese or a drizzle of olive oil.