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 a parchment paper lined baking sheet (or 2). 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, or until cooked through and lightly browned. Set aside until soup is ready.
Meanwhile, for the soup, 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 salt and pepper, and saute 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).
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, garnish with a little fresh parsley and red pepper flakes, if desired.