Combine ground beef, 1/3 cup parmesan cheese, breadcrumbs, egg, garlic, salt, and pepper in a medium bowl.

Moisten hands and shape the meat mixture into 3/4 inch meatballs.

Heat 1 1/2 cups chicken broth and olive oil in a large pot over medium-high heat.

Add meatballs to the pot and simmer until firm, about 5 minutes.

Transfer the meatballs to a bowl using a slotted spoon.

Boil the broth until reduced to a glaze, approximately 6 minutes.

Add celery and onion to the pot and stir until the vegetables soften, about 5 minutes.

Add the remaining 6 cups of chicken broth, pasta, and meatballs (with any accumulated juices).

Reduce the heat to low.

Simmer until the pasta is tender, around 10 minutes.

Add the escarole and simmer until wilted, about 5 minutes.

Season the soup with salt and pepper to taste.

Ladle the soup into individual bowls.

Serve with the remaining 1 cup of parmesan cheese.