In a large mixing bowl, combine the ground beef, breadcrumbs, grated Parmesan cheese, the egg, minced garlic, black pepper, sea salt, and Italian seasoning. Use your hands or a spatula to mix until just combined; be careful not to overwork the meat to keep the meatballs tender.
Shape the mixture into small meatballs, roughly 1 inch in diameter. You should end up with about 16 to 20 meatballs, depending on your exact sizes.
In a large pot or Dutch oven, heat the olive oil over medium heat. Once hot, add the diced onion, sliced carrots, and diced celery, sautéing for about 5-7 minutes until the vegetables are softened and fragrant.
Add the formed meatballs to the pot, browning them gently on all sides for approximately 5 minutes; this step adds depth of flavor to the soup.
Carefully pour in the beef broth and the canned diced tomatoes along with their juice. Stir everything together to combine and bring the soup to a gentle simmer.
Once simmering, add the chopped green beans, continuing to simmer for an additional 10-15 minutes. This will ensure the meatballs are cooked through and the vegetables are tender while the flavors marry beautifully.
Just before serving, stir in the torn spinach (or kale) and cook for another 2 minutes until the greens are wilted and vibrant.
Taste the soup and adjust the seasonings to your liking, adding more salt or pepper if needed.
Serve the hearty soup hot, garnished with a sprinkle of fresh parsley for a burst of color and flavor enhancement.
Notes
Serve with fresh crusty bread and a drizzle of olive oil for added richness.