Cook the Pasta: Bring a large pot of salted water to a boil. Add penne and cook until al dente, about 10-12 minutes. Reserve 1/4 cup pasta water, drain and set aside.

Sauté the Shrimp: Season shrimp with half of Italian seasoning, salt, and pepper. Melt butter in a skillet, add shrimp, and sauté for 4-6 minutes until opaque. Remove and keep warm.

Sauté Aromatics: In the same skillet, melt another tablespoon of butter. Add onion and cook for 4-5 minutes. Stir in garlic and crushed red pepper flakes, cooking until fragrant.

Make the Sauce Base: Sprinkle flour over onion mixture, cooking until lightly browned. Gradually whisk in broth. Add sun-dried tomatoes, tomato paste, and remaining seasoning.

Create Creaminess: Stir in cream and milk until combined. Add Parmesan cheese, whisk until melted. Fold in spinach and wilt.

Combine and Serve: Toss pasta with reserved water in the skillet. Fold in shrimp, mix and serve hot garnished with basil and extra Parmesan.