Bring a large pot of generously salted water to a rolling boil over high heat. Add the fettuccine and cook according to the package directions until al dente, usually about 10 to 12 minutes. Reserve 1/2 cup of the starchy pasta water in a small mug before draining the noodles.

While the pasta is cooking, melt the unsalted butter in a large skillet or saucepan over medium-low heat. Once the butter is completely melted and slightly bubbling, add the minced garlic. Sauté for about 1 minute until highly fragrant, being very careful not to let the garlic brown or burn.

Slowly pour the heavy whipping cream into the skillet, stirring constantly to combine it with the garlic butter. Allow the mixture to come to a gentle simmer, then reduce the heat to low. Let it gently bubble for 3 to 4 minutes until the liquid begins to slightly thicken.

Gradually whisk the freshly grated Parmesan cheese into the simmering cream mixture. Continue whisking gently until the cheese is completely melted and the sauce is smooth, velvety, and homogenous. Stir in the salt and freshly ground black pepper, adjusting seasoning to your taste.

Add the warm, drained fettuccine directly into the skillet with the Alfredo sauce, tossing vigorously with tongs to coat every noodle. If the sauce seems too thick or heavy, splash in a little of the reserved pasta water a tablespoon at a time until you reach your desired creamy consistency.

Serve immediately while hot, as Alfredo sauce tends to thicken and set further as it cools. Garnish with freshly chopped parsley and an extra sprinkle of Parmesan cheese for a beautiful, restaurant-worthy presentation.