How do I make a beurre blanc without it splitting?

Beurre blanc is butter emulsified into an acidic reduction, held together by the milk proteins in the butter itself. It has no egg, which makes it lighter and cleaner than hollandaise, and it is arguably more temperamental, because there is less emulsifier holding a lot of fat. Cream is the insurance most home versions use and it is worth using.

What you'll need

• Dry white wine
• White wine vinegar
• Shallot
• Cold unsalted butter
• Double cream (optional)
• Heavy-based small pan

Step by step

1. Reduce wine, vinegar and shallot to a syrupy couple of tablespoons.100ml dry white wine, 2 tablespoons of white wine vinegar and a finely chopped shallot, simmered until almost all the liquid has gone. This is where the flavour comes from and it also lowers the pH, which helps the emulsion.
2. Add two tablespoons of double cream and bring it back to a simmer.Not classical, and worth doing every time at home. The milk proteins in the cream act as an extra emulsifier and make the sauce far more forgiving of a moment's inattention.
3. Turn the heat right down, or take the pan off entirely.From here the sauce must never boil. If your smallest ring is still too fierce, work off the heat and return the pan for a few seconds at a time.
4. Whisk in cold diced butter two or three cubes at a time.150–200g for the quantities above, cut into 1cm cubes straight from the fridge. Cold butter melts slowly enough to emulsify as it goes. Wait until each addition has almost disappeared before adding the next.
5. Watch the consistency and stop when it coats a spoon.The finished sauce should be pale, glossy, and thick enough to coat the back of a spoon without being heavy. More butter makes it richer but also more fragile.
6. Strain out the shallot if you want a smooth sauce, then season.Salt, white pepper, and a squeeze of lemon if it needs lifting. Straining is optional — many people prefer to leave the shallot in.
7. Serve within about half an hour, kept just warm.A warmed flask works here as it does for hollandaise. It cannot be refrigerated and brought back, so make what you will use.

Tips

• The reduction can be made hours ahead and left in the pan. The butter stage takes five minutes, so all the timing pressure is at the end.
• If the sauce starts to look oily at the edge, take the pan off the heat and whisk in one more cold cube of butter. The cold cube pulls the temperature down and re-tightens the emulsion.
• A split beurre blanc can be rebuilt: put a tablespoon of cream or of the reduction in a clean pan, warm it, and whisk the split sauce into it a spoonful at a time.
• Salted butter is fine here if you season carefully at the end, though unsalted gives you more control over a reduction that concentrates as it goes.
• The classic partners are poached or pan-fried white fish, salmon, asparagus and new potatoes. It is too rich for anything already fatty.

Common mistakes

• Letting the pan boil once the butter has started going in — Boiling drives the emulsion apart and the butter separates out as clear oil. Once it boils there is usually no way back short of a full rebuild.
• Using soft or melted butter — It goes in as oil rather than as a slowly releasing solid, so it never gets broken into droplets. Cold and diced is functional, not fussy.
• Trying to keep it hot — This is a 50–60°C sauce. Held over direct heat or in a hot oven it separates within minutes. Warm is the target, not hot.
• Refrigerating leftovers to reheat — Chilling crystallises the butterfat inside the droplets and punctures the emulsion from the inside. It cannot be brought back by reheating.

Questions people ask