Split sauce

A split sauce, also called a broken sauce, is an emulsion that has come apart. Instead of being smooth and creamy, it looks oily, curdled or thin, with pools of fat on top. It happens most to mayonnaise, hollandaise, beurre blanc, butter-finished pan sauces and ganache.

How to do it

To fix a split cold sauce, such as mayonnaise or aioli:

1. Put 1 egg yolk, or 1 teaspoon of mustard with 1 teaspoon of water, in a clean bowl.
2. Whisk in the broken sauce a few drops at a time.
3. Once it thickens, add the rest in a thin stream.

To fix a split warm sauce, such as hollandaise or béarnaise:

1. Put 1 tablespoon of warm water, or a fresh egg yolk, in a clean bowl.
2. Whisk the broken sauce into it slowly, a spoonful at a time, off the heat.

To fix a split butter sauce, such as beurre blanc:

1. Take it off the heat.
2. Whisk in 1 to 2 tablespoons of cold cream or water to bring the temperature down, then whisk well.

Why it works

An emulsion holds tiny drops of fat apart in water with the help of emulsifiers. If there is too much fat for the water, if the fat goes in too fast, or if the temperature is wrong, the drops join together and separate out. Starting again with a little fresh water or emulsifier gives the fat somewhere to go.

Common mistakes

• Adding oil or butter too fast at the start.
• Letting a warm butter sauce get too hot. Many start to split above about 60°C (140°F).
• Letting a warm butter sauce get too cold, so the butter sets.
• Adding more and more oil to a sauce that is already very thick. Thin it with a little water first.
• Trying to fix it by whisking harder in the same bowl. Start a new base.

In recipes

"Split", "broken", "separated" and "curdled" are often used for the same thing. Strictly, curdling is proteins clumping in dairy or egg sauces from heat or acid, which looks grainy rather than oily.