If you’ve ever made béchamel, clam chowder, or any other flour-thickened sauce or soup, you’ve probably spent time trying to skim off the skin that forms on the surface as it cools. Removing this unappetizing skin can be tricky since it tends to break up and create lumps in your otherwise perfectly smooth mixture. The best way to deal with this annoyance is to stop the skin from forming in the first place.
Protect the surface of a sauce or soup with a thin layer of butter. While the liquid is still warm, lightly dab the top with a pat of butter until there’s a thin sheen of melted butter over the entire sauce. This protective layer keeps the surface soft and skinless. Restaurant chefs often apply the same principle to large batches of soup or sauce by gently ladling a thin layer of melted butter onto the surface. When it’s time to reheat and serve the sauce, simply stir in the butter.
A second method, without butter, requires close monitoring. If you don’t mind tending to your sauce or soup as it cools, you can also prevent a skin from forming by stirring it constantly until it’s completely cool. The action of your whisk or spoon doesn’t allow the skin a flat surface to form on. Stirring also helps speed cooling.