Bring a large pot of salted water to a boil.
Add the spaghetti and let it cook until al dente, according to package instructions.
Drain the pasta and reserve about 1/4 cup of pasta water for later.
Season the shrimp with salt, pepper, and Cajun seasoning.
In a large skillet, melt the butter with olive oil over medium heat.
Add the shrimp and cook for about 2 minutes per side until pink and opaque.
Remove the shrimp from the skillet and set them aside.
In the same skillet, add minced garlic and sauté for about 30 seconds until fragrant.
Pour in the heavy cream and bring it to a gentle simmer.
Stir in the Parmesan cheese until it melts and combines into a creamy sauce.
Add salt and pepper to your taste.
Mix in the reserved pasta water to adjust the sauce consistency as needed.
Return the cooked shrimp and drained spaghetti to the skillet.
Toss everything together until well coated in the sauce.
Sprinkle with fresh parsley for a pop of color and flavor.