In a medium saucepan, warm butter over medium-high heat. Add garlic and cook until fragrant (about 30 seconds). Pour in the cream, reduce heat to medium and cook, stirring frequently, until you see steam coming up from the surface (about 3 minutes). Don’t bring the mixture to a boil.
Gradually whisk in Parmesan cheese, and continue to cook, whisking frequently, until creamy and slightly thickened (about 3 minutes). Stir in nutmeg, then season to taste with salt and pepper.
At this point you can use this Alfredo sauce with any pasta or gnocchi. I like to reserve a little pasta cooking water to thin out the sauce as needed. Always check for seasoning one last time after you toss the pasta with the sauce.