Bring a large pot of salted water to a boil. Add the pasta and cook according to package instructions until al dente. Reserve 1 cup of the pasta water, then drain the pasta.
Meanwhile, add the oil and 1 tablespoon of the butter to a large skillet over medium heat. Add the shrimp and cook for about a minute. Season with the salt, pepper, and Old Bay (if using).
Continue to cook the shrimp until pink and opaque (about another minute or two). Remove the shrimp to a plate and set aside.
Add the remaining 1/2 tablespoon of butter to the skillet. Add the garlic and cook for 30 seconds or until fragrant.
Stir in the heavy cream and scrape up any browned bits from the bottom of the pan. Let it bubble for a minute.
Stir in the parmesan cheese. Let it melt, then add a splash of the reserved pasta water to loosen the sauce up a bit. Taste and season with extra salt & pepper if needed.
Add the cooked pasta and shrimp to the skillet and toss until well coated and heated through. Garnish with the parsley and serve immediately.