Bring a large pot of salted water to a boil over high heat. Add the fettuccine and cook until al dente according to the package directions. Drain.
Meanwhile, melt the butter in a large saucepan over medium-high heat. Add the garlic, garlic powder, nutmeg, salt, and pepper and cook, stirring, until the garlic is fragrant, about 1 minute.
Slowly stir in the heavy cream and bring to a simmer. Add the Parmesan and simmer, stirring, until fully incorporated, about 2 minutes. Reduce the heat to medium-low and simmer until thickened, about 5 minutes more.
Remove the pot from heat. Add the fettuccine and toss to coat. Garnish with fresh parsley and serve.