How to Make It
In a large bowl, stir the ricotta and 1/4 cup of grated Parmigiano with the egg, breadcrumbs, nutmeg, 1 teaspoon salt, 1/2 teaspoon pepper and 1/4 cup of water. Add the pork and combine. Form into 12 meatballs.
In a large enameled cast-iron casserole, heat the olive oil. Add the meatballs and cook over moderate heat, turning, until golden all over, about 10 minutes. Stir in the broth and the piece of cheese. Cover and simmer gently over moderate heat, stirring occasionally, until the meatballs are cooked through and the broth is slightly reduced, about 20 minutes. Stir in the peas and spinach, season with salt and pepper and simmer until the peas are warmed through.
In shallow bowls, spoon the meatballs and broth over egg noodles. Garnish with grated Parmigiano and serve.