Cook the Pasta: Bring a large pot of heavily salted water to a boil. Add the penne pasta and cook according to package directions until al dente, usually 9-11 minutes. Reserve 1/4 cup of pasta water, then drain and set aside.

Sauté the Shrimp: In a large skillet, melt 2 tablespoons of unsalted butter. Season shrimp with salt, pepper, and Italian seasoning, then cook for 4-6 minutes until opaque. Remove and keep warm.

Prepare the Sauce Base: In the same skillet, melt an additional tablespoon of butter. Sauté finely chopped onion for 4-5 minutes, add minced garlic and crushed red pepper, cooking until aromatic.

Create the Roux: Sprinkle 2 tablespoons of all-purpose flour into the skillet, stirring constantly for 1-2 minutes until slightly golden. Gradually whisk in 1 cup of chicken or vegetable broth.

Build the Creamy Sauce: Add sun-dried tomatoes and tomato paste to the skillet, simmer for 2-3 minutes until the sauce thickens.

Add Creaminess: Pour in 1/2 cup of heavy whipping cream and 1/4 cup of whole milk, stir until combined, then add Parmesan cheese and spinach, cooking until wilted.

Combine the Dish: Add drained penne pasta to the sauce, tossing to coat. Mix in reserved pasta water as needed, fold in shrimp and heat through.

Plate and Garnish: Serve in warm bowls or on plates, garnishing with additional Parmesan and fresh basil. Drizzle with olive oil for elegance.