Why starting again works
An emulsion breaks when the droplets of fat merge back together, usually because fat was added faster than the emulsifier could coat it, or because heat or cold pushed it past what it could hold.
The fat and the water are still there and still perfectly good. What is gone is the arrangement. So the fix is not to add anything to the broken sauce but to build a fresh emulsion and feed the broken one into it slowly — exactly as you fed the oil in the first time.
The new emulsion has plenty of emulsifier and very little fat, so it can absorb the broken mixture a drop at a time, and each drop is incorporated before the next arrives.
The rescue
The same seven steps for every sauce in the family.
- Stop immediately. Take the pan or bowl off any heat and stop adding fat.
- Take a clean bowl and put in something to build around: a fresh egg yolk for mayonnaise or hollandaise, a teaspoon of mustard for a vinaigrette, or a tablespoon of warm water for anything.
- Whisk that on its own for a few seconds.
- Add the broken sauce a few drops at a time, whisking hard between each addition. This first stage is slow and it is the whole rescue.
- Watch for the moment it thickens and turns opaque. That is the emulsion forming.
- Once it has, add the rest of the broken sauce in a thin steady stream, still whisking.
- Taste and re-season. A rescued sauce usually needs more salt and acid than you expect.
What to build around, by sauce
- Mayonnaise
- A fresh egg yolk, or a teaspoon of mustard, or a tablespoon of warm water.
- Hollandaise and béarnaise
- A tablespoon of hot water, or a fresh yolk for a bad split. Sieve afterwards if it was overheated and grainy.
- Beurre blanc
- A tablespoon of cream or a splash of the reduction, whisked over very low heat, then cold butter beaten in.
- Vinaigrette
- A teaspoon of mustard, or a little honey. The easiest of the family to rebuild.
- Cream sauce
- A splash of cold cream or a knob of cold butter whisked in off the heat. Often no need to start again.
- Pan sauce
- A splash of stock or water off the heat, whisked hard, then cold butter.
The shortcuts that also work
- A stick blender in a tall narrow jug. Rescues almost anything mechanically by shearing the fat into small droplets again. Least elegant, most reliable.
- A teaspoon of cornflour slaked in cold water, whisked into a warm split cream sauce. The starch stabilises it.
- Cold butter into a hot broken butter sauce, which often brings it back on its own.
- Sieving, for an overheated sauce with set curds in it. Rescue first, then sieve.
- Accepting it. A split vinaigrette is fine — shake it and dress the salad immediately.
- Never adding more fat to a broken emulsion. It makes it worse every time.
Common questions
Why does starting again work?
The fresh emulsifier has almost no fat to hold, so it can take the broken mixture a drop at a time.
How slowly do I have to add it?
Drops, for the first spoonful or two. After it thickens you can go much faster.
Does a stick blender really rescue it?
Yes, almost always. It shears the fat back into small droplets mechanically.
Can I save an overheated hollandaise?
Usually, and sieve the rescued sauce to remove the curds the heat set.
Should I add more oil to fix it?
Never. That is what broke it.
Try this next
- Emulsifying how the emulsion is built
- Split mayonnaise the cold case
- Split hollandaise the hot case
- Emulsion breakage why it splits