Remove the sausage from its casings and crumble it into a heavy-bottomed Dutch oven set over medium-high heat.
Cook the sausage for about 5 minutes, breaking it up with a wooden spoon, until browned.
Add the chopped onion and frozen corn and sauté for about 10 minutes until the onion is softened and the corn is warmed through.
Stir in the dry orzo and the chicken broth, bring the mixture to a boil, then reduce heat to medium-low.
Simmer for 10 minutes, stirring every few minutes and scraping the bottom to prevent sticking, until the orzo is tender and most liquid is absorbed.
Remove the pot from the heat, add the packed spinach, stir to combine, and cover for 2–3 minutes until the spinach is wilted.
Stir in the grated Parmesan, season with freshly ground black pepper to taste, and serve immediately.