1. Cook the pasta in a large pot of generously salted boiling water until al dente according to package directions, then reserve 1/2 cup of the starchy cooking water and drain the pasta.

2. Pat the shrimp very dry with paper towels, then season them lightly with a pinch of salt and black pepper.

3. Heat the olive oil and 1 tablespoon of the butter in a large skillet over medium-high heat, then cook the shrimp in a single layer for 1–2 minutes per side until opaque and lightly golden; transfer them to a plate.

4. Reduce the heat to medium, add the remaining tablespoon of butter to the skillet, then stir in the minced garlic and crushed red pepper flakes and sauté just until fragrant, about 30 seconds.

5. Pour in the white wine or chicken broth, scraping up any browned bits from the bottom of the pan, and let the liquid simmer for 2–3 minutes until reduced by about half.

6. Stir in the heavy cream, Italian seasoning, salt, and black pepper, then simmer the sauce gently for 3–4 minutes, stirring often, until it thickens slightly.

7. Add the grated Parmesan cheese and stir until melted and smooth, then toss in the cooked pasta, shrimp, lemon juice, lemon zest, and chopped spinach, loosening the sauce with a splash of reserved pasta water as needed so it coats everything.

8. Taste and adjust the seasoning, then sprinkle the pasta with fresh parsley and extra Parmesan before serving hot.