Unless, that is, the sauce breaks.
Suddenly, the fat separates out to form oily pools that taste greasy, and some of the solids in the sauce may even curdle. The whole thing looks and tastes like a mess.
But as it turns out, there is an easy way to fix this problem and rescue your sauce. So step away from the cornstarch or flour because thickeners will not help.
Instead, just add water.
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Why Do Sauces Break?
A pan sauce is an example of a fat-in-water emulsion. You build the sauce by deglazing meat drippings or fond in a pan with stock or wine and then whisking in fat, usually in the form of butter or cream.
When the tiny droplets of butterfat (aided by the agitation of whisking) get suspended in liquid, the result is a shiny, creamy sauce.
However, if the sauce stays on the heat too long and too much water evaporates, it will break, since there’s no longer enough water to hold the fat in suspension. If this happens, the sauce will look curdled and greasy.
The Fix Is Simple—Add Water Back.
While it may seem counterintuitive to add liquid to an oily sauce, whisking in more water replaces what was evaporated and helps re-suspend that fat, emulsifying your sauce once more.
A generous splash of water is all it takes.
Here’s how fix a broken sauce: Add about ¼ cup of water to the pan and reheat the sauce to a vigorous simmer, whisking constantly. The bubbling action will help re-emulsify the butter and bring back that thick, glossy sauce. Continue simmering until the sauce reaches the desired consistency, then serve.