1. Bring a large pot of salted water to a boil and cook the pasta until al dente, about 8 to 10 minutes.

2. Reserve 1/2 cup of pasta water and drain the pasta.

3. While the pasta cooks, melt 2 tablespoons of butter with olive oil in a large skillet over medium heat.

4. Add minced garlic and sauté for 30 seconds until fragrant.

5. Add shrimp in a single layer and cook 1 to 2 minutes per side until pink and opaque.

6. Season shrimp with salt, pepper, and red chili flakes if using, then remove shrimp and set aside.

7. Lower heat, add remaining butter, and scrape up browned bits from the skillet.

8. Stir in lemon juice and 1/4 cup reserved pasta water to form the sauce.

9. Add drained pasta and cooked shrimp to the skillet and toss to coat, adding more pasta water as needed.

10. Stir in chopped parsley and adjust seasoning to taste.

11. Serve immediately with grated parmesan cheese if desired.