Which cream can I boil without it splitting?

The reason so many home cream sauces split is that British cream is sold in legally defined fat classes and the recipes do not say which one to use. Fat is what keeps the milk proteins apart as water leaves during reduction. Below about 30 per cent there is not enough of it, and the proteins clump into visible grains.

Step by step

1. Read the pot: the fat class is the whole answer.UK cream names are legally defined by minimum fat: double cream at least 48 per cent, whipping cream at least 35 per cent, single cream at least 18 per cent, half cream at least 12 per cent. Crème fraîche is typically around 30 per cent. That number predicts behaviour exactly.
2. Above the line — double and whipping cream — reduce freely.Both can be brought to a boil and simmered down to thicken a sauce without splitting. Double cream is the safe default for any sauce that has to reduce, and it thickens noticeably as it goes.
3. At the line — crème fraîche — heat gently only.It is stabilised by its culture as well as by fat and tolerates a gentle simmer, but it will split if boiled hard or held bubbling. Stir it in near the end and keep the heat low.
4. Below the line — single, soured, yoghurt, milk — add off the heat.Single cream splits readily and is behind a large share of failed home cream sauces. Take the pan off the hob, stir the cream in, and return it only to a warm heat, never a simmer.
5. Or stabilise a low-fat dairy with starch.A teaspoon of cornflour whisked into 150ml of single cream, soured cream or yoghurt before it goes in physically separates the proteins as they heat. This is what a béchamel is doing for milk, and it is why milk sauces do not curdle.
6. Add acid and salt last, off the heat.Both lower the temperature at which dairy splits. A wine, lemon or tomato sauce is much harsher on cream than a plain one, so a sauce with acid in it wants double cream and wants the acid added at the end.
7. Reduce first, add cream second.The most robust way to build a cream sauce is to reduce the stock or wine to where you want it, then add the cream and simmer only briefly. That way the dairy spends the minimum time on the heat.

Tips

• Extra thick double cream has been homogenised to a spoonable texture and does not behave the same in a pan. Buy pouring double cream for sauces.
• Cream sold as 'single cream alternative' or 'cooking cream' is usually stabilised and boils safely. It is a reasonable choice for a sauce and a poor one for anything eaten cold.
• Whipping and double cream can both be frozen in a sauce; single cream splits on thawing.
• In a pan sauce, cream reduced by a third takes on a noticeably thicker, glossier texture. That is not splitting, it is what you are after.
• Half-fat versions of anything are the least stable options on the shelf. Do not use them for a sauce that will be reduced.

Alternatives

• Double cream: At least 48 per cent fat. Boils, reduces and whips. The safe choice for any sauce and the one to buy if you are only buying one.
• Whipping cream: At least 35 per cent. Reduces safely and whips to a lighter result than double. Slightly cheaper and slightly less rich in a sauce.
• Crème fraîche: Around 30 per cent and cultured, so it brings a pleasant tang. Tolerates gentle heat but splits at a hard boil. Excellent stirred into a sauce at the end.
• Single and soured cream: Around 18 per cent. Will split if boiled. Use off the heat, or stabilise with cornflour. Fine poured over a dessert or stirred into a soup at the table.
• Evaporated milk and plant creams: Evaporated milk is heat-stable because it has been sterilised and homogenised, and it does not split. Oat and soya creams are formulated with stabilisers and generally boil safely; check the pack, since some plain plant milks curdle with acid.

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