Heat the olive oil in a large Dutch oven or heavy pot over medium-high heat. Add the sliced sausage and cook, stirring occasionally, until browned on both sides, about 5 minutes. Use a slotted spoon to transfer the sausage to a plate, leaving the drippings in the pot.

Reduce the heat to medium. Add the onion, bell pepper, and a pinch of salt. Cook until softened, about 4 minutes, scraping up any browned bits from the bottom. Add the garlic and cook for another minute, until fragrant.

Push the vegetables to one side of the pot and add the butter. Let it melt, then sprinkle the flour over the butter and stir to combine. Cook for 1 minute, stirring constantly.

Slowly pour in the chicken broth while whisking to prevent lumps. Add the heavy cream, Cajun seasoning, smoked paprika, and cayenne pepper. Whisk until smooth. Bring the mixture to a gentle simmer.

Stir in the dried pasta and the browned sausage. Make sure the pasta is mostly submerged in the liquid. Cover the pot and let it simmer over medium-low heat, stirring every 2 to 3 minutes, until the pasta is tender and has absorbed most of the sauce. This takes about 12 to 15 minutes, depending on your pasta shape.

Once the pasta is al dente, remove the pot from the heat. Stir in the fresh spinach until it wilts. Then add the Parmesan cheese and stir until melted and creamy. Taste and adjust salt and pepper.

Ladle into bowls, top with extra Parmesan and a sprinkle of fresh parsley if you like.