Heat a large, deep 12-inch skillet or Dutch oven over medium-high heat. Add the Italian sausage and cook for 5-7 minutes, breaking it into bite-sized crumbles with a wooden spoon until deeply browned. Drain excess grease if needed, leaving 1 tablespoon of drippings in the pan.

Add the minced garlic, sliced sun-dried tomatoes, Italian seasoning, and red pepper flakes. Sauté for 1 minute until fragrant.

Pour in the chicken broth and scrape up any browned bits from the bottom of the skillet. Stir in the dry rigatoni pasta and press it down so it is mostly submerged.

Bring the liquid to a boil, then immediately reduce heat to medium-low, cover with a tight-fitting lid, and simmer for 11-13 minutes, stirring halfway through, until the pasta is al dente and most of the broth is absorbed.

Reduce heat to low. Pour in the heavy cream and add the fresh baby spinach, stirring gently for 2 minutes until the spinach wilts and the sauce bubbles into a glossy glaze.

Remove the skillet from the heat and stir in the freshly grated Parmesan cheese and fresh basil until melted and creamy. Serve warm.