01 - Bring a large pot of salted water to a boil. Cook the pasta according to package directions until al dente. Reserve 1/2 cup pasta water, then drain.
02 - Heat olive oil in a large skillet over medium heat. Add the onion and sauté for 3 minutes until softened. Add the garlic and cook an additional minute, stirring frequently.
03 - Add the fresh spinach to the skillet and cook, stirring, until wilted, about 2 to 3 minutes.
04 - Pour in the heavy cream and bring to a gentle simmer. Stir in Parmesan cheese and ground nutmeg. Season with salt and freshly ground black pepper.
05 - Add the drained pasta to the sauce, tossing to coat evenly. Add reserved pasta water as needed to loosen the sauce.
06 - Serve immediately, garnished with extra Parmesan cheese and chopped parsley if desired.