Make the meatballs: Crack the egg into a large bowl and beat it lightly with a fork. Add the beef, pork, bread crumbs, Parmesan, parsley, garlic, oregano, salt and pepper. Mix gently but thoroughly, until incorporated. Coat your hands with olive oil, then form small meatballs using 1 heaping teaspoon of the mixture per meatball; transfer to a plate or sheet pan.

Make the soup: In a large pot or Dutch oven, heat the olive oil over medium heat. When the oil is hot, fry the meatballs in 2 batches, turning occasionally, until mostly browned all over, 3 to 4 minutes. Transfer to a paper towel-lined plate.

Add the onion, carrots and celery to the pot and cook, stirring occasionally, until the vegetables are crisp-tender, about 10 minutes.

Add the garlic, 1 teaspoon of salt (or 2 teaspoons if you’re using low-sodium broth) and ½ teaspoon black pepper. Cook until the garlic is fragrant, about 1 minute.

Return the meatballs to the pot, add the broth and bring to a simmer over medium-high heat. Stir in the pasta, lower the heat and simmer, stirring occasionally, until the pasta is tender, about 10 minutes.

Turn off the heat and stir in the spinach until wilted. Taste and season with salt and pepper, if needed.

Serve hot, topped with Parmesan.