In a saucepot with a tight-fitting lid, melt butter over medium heat. Add orzo and toast to deep golden in color and fragrant. Stir in rice, add about 2 cups of chicken stock and bring to a simmer. Cover and cook 18 minutes, until rice is just tender, stirring occasionally and adding a bit of water as needed if rice begins to stick.
Bring remaining 6 cups stock plus 2 cups water to a boil in a soup pot. Reduce heat to low, rolling simmer.
Season meat with salt and pepper; add ricotta, season with a little freshly grated nutmeg and add breadcrumbs, garlic, egg, grated cheese and EVOO; mix to combine. Use a small scoop to roll 24-30 walnut-sized balls. Add meatballs to broth and simmer 8-10 minutes. Wilt in greens and turn off heat; let stand 2 minutes and serve in shallow bowls.