In a large skillet or saucepan, melt butter over medium-low heat. Add minced garlic and sauté for 1-2 minutes until fragrant but not browned.
Pour in heavy cream and add cream cheese, stirring constantly until the cream cheese is completely melted and incorporated, about 3-4 minutes.
Bring the mixture to a gentle simmer, then reduce heat to low. Do not let it boil.
Gradually add the freshly grated Parmesan cheese, stirring constantly with a whisk or wooden spoon until the cheese is completely melted and the sauce is smooth and creamy, about 3-5 minutes.
Season with salt, pepper, and nutmeg if using. Taste and adjust seasonings as needed.
If the sauce is too thick, add a splash of cream or pasta water to reach desired consistency. Serve immediately over your favorite pasta or use as desired.