Melt the butter in a medium saucepan over medium-low heat.
Add the minced garlic and cook for about 30 seconds, just until fragrant. Do not let the garlic brown.
Pour in the heavy cream.
Add the salt, black pepper, and optional nutmeg.
Bring the mixture to a gentle simmer over medium-low heat. Do not let it boil.
Cook for about 3 to 4 minutes, stirring occasionally, until the cream is hot and slightly reduced.
Reduce the heat to low.
Add the freshly grated Parmesan a little at a time, whisking continuously until each addition melts before adding more.
Continue whisking until the sauce is smooth and coats the back of a spoon.
Do not overcook the sauce because it will thicken slightly as it stands.
Taste and adjust the salt only if needed.
Remove from the heat and let the sauce stand for about 1 minute.
Toss with warm cooked pasta or serve over chicken, vegetables, or another dish.
If the sauce becomes too thick, loosen it with a small amount of warm pasta water.