Bring a large pot of salted water to a boil. Add penne and cook until al dente, about 8-10 minutes. Reserve 1 cup of pasta water before draining. Drain pasta thoroughly and set aside.

Heat 2 tablespoons olive oil in a large skillet over medium heat. Add Italian sausage and cook for 5-7 minutes, breaking it apart with a wooden spoon, until browned and cooked through. Transfer sausage to a plate using a slotted spoon, leaving drippings in pan.

Reduce heat to medium-low and add minced garlic to the same skillet. Sauté for about 1 minute, stirring constantly, until fragrant and lightly golden.

Stir in chopped sun-dried tomatoes, chicken broth, Italian seasoning, and red pepper flakes. Scrape up any browned bits from the bottom. Simmer for 3-5 minutes until slightly reduced.

Pour in heavy cream and stir until well combined. Add freshly grated Parmesan cheese and whisk until melted and smooth. Return browned sausage to skillet along with baby spinach. Cook for 2-3 minutes until spinach wilts. Season with salt and pepper to taste.

Add drained penne to the skillet and toss until pasta is well-coated with sauce. Add reserved pasta water a tablespoon at a time if sauce is too thick. Serve hot, garnished with fresh basil leaves and additional Parmesan.