Q. What's the best way to reheat a cream-based sauce such as alfredo without it separating? I have tried to reheat homemade alfredo and restaurant leftovers, and I always get a buttery, unappetizing mess.
That's definitely a common problem. The fat in the sauce does want to break free. (Too bad it doesn't want to break free from our hips after we eat it, isn't it?)
The most common solution is to add a little milk while you're reheating, and to heat it slowly over low heat. That should make it smoother. If you're making the sauce yourself and you know you'll want to reheat it, you can also try adding a little flour in the beginning. Melt the butter and stir in flour just like making a roux, then proceed with the recipe. That may make the sauce more stable and less like to “break,” or separate, when it's reheated.