In a large Dutch oven or soup pot, heat the olive oil and butter over medium heat. Add the diced onion, chopped shallot, diced celery, and yellow bell pepper, stirring to combine. Cook for about 4-5 minutes until the onions become translucent, stirring occasionally.

Add the minced garlic to the pot, stir well, and cook for an additional 2 minutes.

Pour in the chicken broth, then add the diced carrots, parmesan rind (if using), and kosher salt. Bring the mixture to a boil, then reduce the heat to maintain a steady simmer. Cook uncovered for 20-25 minutes, or until the vegetables are tender.

If you added a parmesan rind, remove it from the pot. Using a slotted spoon, take out 2 cups of the cooked vegetables and set them aside.

Blend the remaining broth and vegetable mixture in the pot until smooth using an immersion blender. If using a regular blender, allow the mixture to cool slightly before blending. Remove the center cap from the blender lid and cover it with a clean kitchen towel or several layers of paper towels to let steam escape.

Add the pastina to the pot and bring the mixture back to a boil. Then reduce to a steady simmer and cook according to the package instructions for the pastina (for example, acini de pepe takes about 9 minutes).

Stir in the reserved chicken and the set-aside vegetables. Mix well to combine.

Cover the pot and let the soup rest for 20 minutes. Taste the soup and adjust the seasoning, adding more salt if necessary.

Serve the soup with grated parmesan on top, a sprinkle of finely chopped fresh rosemary or thyme (or both), and freshly ground black pepper. Enjoy!