In a large pot, bring salted water to a boil and cook the penne pasta according to the package instructions until al dente. Drain and set aside.
In a large skillet, heat olive oil over medium heat. Remove the casing from the Italian sausage and add it to the skillet, cooking until browned and fully cooked, about 5-7 minutes.
Add minced garlic to the skillet and sauté for an additional minute until fragrant.
Reduce heat to low and stir in the heavy cream, allowing it to simmer for 2-3 minutes while stirring.
Mix in fresh spinach, cherry tomatoes, and Italian seasoning. Cook for another 2-3 minutes until the spinach wilts and the tomatoes soften.
Add the cooked penne pasta to the skillet, tossing well to coat the pasta in the creamy sauce. Season with salt and pepper to taste.
Stir in grated Parmesan cheese until melted and combined. If the sauce is too thick, add a splash of pasta water to reach the desired consistency.
Serve immediately, garnished with fresh basil leaves if desired.