Melt 1/2 cup unsalted butter in a saucepan over medium-low heat
Add 2 cups heavy cream and stir until combined
Simmer gently for 3 to 5 minutes, stirring often
Add 2 cups freshly grated Parmesan cheese gradually
Stir until the cheese melts and the sauce becomes smooth
Add 1 to 2 cloves minced garlic if desired
Season with salt to taste
Add black pepper to taste
Add a pinch of nutmeg if desired
Remove from heat when the sauce is thick and creamy
Toss with cooked pasta immediately
Add reserved pasta water a little at a time if the sauce is too thick