Bring a large pot of salted water to a boil. In a skillet over medium-high heat, brown the ground beef with 1/4 tsp salt and the pepper, about 6 minutes, then transfer to a plate.

Cook the fettuccine in the boiling water until al dente, reserve 1 cup pasta water, then drain.

In the same skillet over medium heat, melt the butter and cook the garlic for 30 seconds. Add the heavy cream and simmer for 2 minutes, scraping up browned bits.

Remove from heat, stir in the Parmesan in batches with the remaining 1/4 tsp salt and nutmeg. Return the beef and pasta to the pan, toss with tongs, and add pasta water as needed to coat.

Plate into bowls and top with fresh parsley.