1. Bring a large pot of salted water to a boil, add the pasta, and cook according to package directions until just al dente. Before draining, reserve about 1 cup of the starchy pasta cooking water, then drain the pasta and set it aside.

2. While the pasta cooks, pat the shrimp dry with paper towels, then season them with about 1/4 teaspoon salt, 1/4 teaspoon black pepper, and a pinch of Italian seasoning.

3. Heat 1 tablespoon butter and the olive oil in a large deep skillet over medium high heat. Add the seasoned shrimp in a single layer and cook for 1 to 2 minutes per side, just until they turn pink and opaque. Transfer the shrimp to a plate and set aside.

4. Reduce the heat to medium and add the remaining 1 tablespoon butter to the same skillet. Stir in the minced shallot and cook for 2 to 3 minutes until softened and fragrant.

5. Add the minced garlic and red pepper flakes and cook for 30 seconds to 1 minute, stirring constantly, just until the garlic is fragrant but not browned.

6. Pour in the white wine or chicken broth to deglaze the pan, scraping up any browned bits from the bottom with a wooden spoon. Let the liquid simmer for 2 to 3 minutes until slightly reduced.

7. Stir in the heavy cream and 1/4 cup of the reserved pasta water. Bring the mixture to a gentle simmer over medium low heat and cook for 3 to 4 minutes, stirring occasionally, until the sauce begins to thicken.

8. Add the Italian seasoning and gradually stir in the grated parmesan cheese, a small handful at a time, until it melts smoothly into the sauce. If the sauce becomes too thick, add more reserved pasta water a splash at a time until it reaches a silky, pourable consistency.

9. Return the cooked shrimp and any accumulated juices to the skillet, stirring to coat them in the creamy garlic sauce. Cook for 1 to 2 minutes, just until the shrimp are heated through.

10. Add the drained pasta directly to the skillet and toss well so every strand is coated in the sauce. Stir in the lemon juice, lemon zest, and baby spinach if using, allowing the spinach to wilt slightly in the heat.

11. Taste and adjust the seasoning with additional salt, black pepper, or red pepper flakes as desired. If needed, thin the sauce with an extra splash of pasta water until it is as creamy as you like.

12. Remove from the heat and garnish with chopped fresh parsley or basil and extra parmesan cheese before serving warm.