Bring a large pot of salted water to a boil. Add the fettuccine and cook according to the package directions until al dente. Drain and return to the pot off the heat.
While the water comes to a boil, place a medium saucepan (or skillet) over medium heat. Add the butter and cook until melted. Add the garlic and cook for 2 minutes, stirring frequently to prevent burning.
Add the cream cheese and stir to combine. Cook until the cheese has become very soft, about 3 to 5 minutes. Add in the cream and Parmesan cheese. Whisk to combine until the cream cheese is dissolved into the sauce.
Continue cooking the sauce until it begins to bubble and the Parmesan is melted, about 3 minutes. Reduce the heat to medium-low and continue to simmer, stirring occasionally, until the sauce has thickened a bit. This takes about 10 to 12 minutes.
Remove sauce from heat and whisk in salt, pepper, and nutmeg. Check seasonings and adjust to your taste.
Add 1/2 to 2/3 of the sauce to the fettuccine and toss to coat. Garnish with shaved parmesan and chopped parsley if desired.
This recipe makes 3 cups of alfredo sauce. I don't usually use it all for the pasta. Save the extra for turning a red sauce into a rosa sauce, dipping bread into, or use it for casseroles and pizza sauce.
You can also add cooked chicken, shrimp, meatballs, or bacon for some protein. Broccoli, asparagus, and bell peppers are all great veggie add-ins too.