Cook the penne pasta according to package instructions until al dente. Drain and set aside, reserving 1/2 cup of pasta water.
In a large skillet, heat the olive oil over medium heat. Add the Italian sausage and cook until browned, breaking it up with a spoon, about 5-7 minutes.
Add the minced garlic and cherry tomatoes to the skillet. Sauté for another 2-3 minutes until the tomatoes soften.
Pour in the heavy cream and stir in the Italian seasoning. Bring to a gentle simmer, allowing the sauce to thicken slightly, about 3-5 minutes.
Add the spinach leaves and cook until wilted, about 2 minutes.
Stir in the cooked penne pasta and Parmesan cheese, mixing well. If the sauce is too thick, add reserved pasta water a little at a time until desired consistency is reached.
Season with salt and pepper to taste. Serve hot, garnished with fresh basil if desired.