Heat the olive oil in a large pot or Dutch oven over medium heat. Add the onion, carrots, celery, ½ teaspoon of the salt, and pepper. Cook, stirring occasionally, for 8 to 10 minutes, or until softened.

Stir in the garlic, then add the thyme and parsley bundles, bay leaves, Parmesan rind, broth, and the remaining ¾ teaspoon salt. Stir, then bring to a boil. Reduce the heat to maintain a simmer and cook, uncovered, for 25 to 30 minutes, or until the vegetables are tender. Remove and discard the Parmesan rind, bay leaves, and thyme and parsley bundles.

Use a slotted spoon to scoop 2 cups of the vegetables out of the pot. Transfer to a blender and add 1 cup of the broth. Allow to cool slightly, then blend until completely smooth. Stir the puree back into the pot.

Bring the soup to a vigorous simmer. Add the pastina and cook until tender, about 9 to 15 minutes depending on the type of pasta you’re using. Stir in the lemon juice and season to taste.

Serve topped with freshly grated Parmesan and chopped fresh parsley leaves.