Cook the Pasta: Bring a large pot of salted water to a boil. Cook the fettuccine according to the package instructions until al dente. Reserve 1/2 cup of pasta water and drain the rest.

Prepare the Sauce: In a large skillet over medium heat, melt the butter. Add the heavy cream and bring to a gentle simmer, stirring frequently.

Incorporate Cheese: Gradually add the Parmesan cheese, stirring constantly, until the sauce is smooth and creamy. Season with salt and pepper.

Combine Pasta and Sauce: Add the drained fettuccine to the skillet with the sauce. Toss to coat, adding reserved pasta water as needed to achieve the desired consistency.

Serve: Transfer to serving plates, garnish with freshly chopped parsley (if using), and serve immediately.