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 and cooked through.
Add the chopped onion and the frozen corn to the pot and sauté for about 10 minutes until the onion is softened and the corn is heated through.
Stir in the dry orzo and pour in the chicken broth; stir to combine and bring the mixture to a boil.
Reduce the heat to medium-low and 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, stir in the packed baby spinach until wilted, then cover the pot for a couple minutes to finish wilting.
Top with the freshly grated Parmesan and freshly ground black pepper to taste, then serve.