Cook fettuccine according to package directions. Reserve 1 cup pasta water before draining.
Melt butter in a large skillet over medium heat. Add garlic and cook 1 minute until fragrant.
Pour in heavy cream and bring to a gentle simmer. Cook 3-4 minutes until slightly thickened.
Remove skillet from heat and stir in Parmesan, salt, pepper, and nutmeg until smooth.
Add drained pasta and toss, adding pasta water a little at a time until sauce coats the noodles evenly.
Serve immediately with extra Parmesan and fresh parsley.