If using homemade meatballs, pan fry in a little bit of oil over medium-high heat for 2-3 minutes per side to form a crust.
Start the pasta water to boil around the same time as you start the soup base.
In a dutch oven or similar deep pot, heat a little olive oil over medium heat.
Add the onion and fennel, cook for about 4 minutes and the veggies are softened.
Add the garlic, cook for another 1-2 minutes.
Add in the spinach, allow to wilt for 1 minute.
Add the stock (and herbs for store-bought). Bring to a light simmer, reduce heat and allow to cook for 15-20 minutes.
Add the meatballs about half way through the cook time.
Cook the pasta per package instructions in salted water.
Add the pasta to the soup at the end and serve.