Preheat oven to 350 degrees.
In a bowl, combine all of the 'for the meatballs' ingredients. Using your hands, gently combine.
With a melon baller or a teaspoon, drop ~1 - 1 1/4 inch balls onto two parchment paper lined baking sheets. Using your hands, go back through and roll the meatballs into round circles, they don't have to be perfect.
Place in oven and bake for 30 minutes (swap placement of trays halfway through), or until cooked through and lightly browned. Set aside until soup is ready.
While the meatballs bake, heat olive oil over medium-high heat in a dutch oven or large soup pot.
Add the onions, celery, carrots, red pepper flakes, and garlic. Season with a little salt and pepper, and sauté until softened, about 5-7 minutes.
Add the chicken broth and lemon juice and bring to a boil. Then, reduce heat to a low simmer (medium-low heat or low heat depending on your stovetop). Simmer for about 10-20 minutes (or until meatballs are done).
Add the parsley, oregano, and the leafy greens. Stir until just wilted.
Add the cooked meatballs into the soup, taste and add salt and pepper, to taste.
Ladle soup into bowls, sprinkle with parmesan and enjoy!