01 - Bring a large pot of salted water to a boil and cook the pasta until al dente following package instructions. Reserve ½ cup of pasta water, then drain and set aside.
02 - Heat unsalted butter in a large skillet over medium heat; add minced garlic and sauté for 30 seconds until fragrant.
03 - Add chopped spinach to the skillet and cook for 2 to 3 minutes, stirring continuously until the spinach has wilted.
04 - Reduce heat to low, then add heavy cream, cream cheese, mozzarella, and Parmesan. Stir gently until the cheeses melt completely and the sauce becomes smooth.
05 - Incorporate salt, freshly ground black pepper, and nutmeg if desired, adjusting seasoning to taste.
06 - Add the cooked pasta into the skillet and toss thoroughly to coat with the cheese sauce. Use reserved pasta water in small increments if additional creaminess is needed.
07 - Serve immediately, garnished with fresh basil leaves or additional Parmesan cheese as preferred.