In a large bowl, gently combine the ground beef, panko breadcrumbs, grated Parmesan cheese, egg, minced garlic, Italian seasoning, salt, and black pepper. Mix until just combined.

Roll the mixture into small, uniform meatballs, about 1-inch in diameter. Heat olive oil in a large Dutch oven or soup pot over medium-high heat and brown the meatballs on all sides. Remove the browned meatballs to a plate and set aside.

Reduce the heat to medium and add more olive oil if needed. Add the diced onion, carrots, and celery. Sauté for 5-7 minutes until softened and translucent.

Stir in the minced garlic and tomato paste. Cook for another 1-2 minutes until the garlic is fragrant and the tomato paste has deepened in color.

Pour in the broth and scrape up any browned bits from the bottom of the pot. Stir in Italian seasoning, salt, and black pepper. Bring the soup to a gentle simmer.

Carefully add the browned meatballs back into the soup. If cooking the pasta directly in the soup, add the small pasta now. Simmer for 8-10 minutes until the pasta is al dente and the meatballs are cooked through.

Reduce the heat to low and stir in the heavy cream and fresh spinach. Cook for 1-2 minutes until the spinach has wilted and the soup is heated through.

Taste the soup and adjust seasonings as needed. Ladle hot soup into bowls, garnish with extra grated Parmesan cheese and fresh chopped parsley or basil, and serve immediately.