Why is my custard lumpy or thin?
Custard is scrambled egg waiting to happen — tempering and gentle heat are the whole technique.
- Difficulty
- intermediate
- Time
- 25 min
- Read
- 2 min
Short answer
Lumpy custard is scrambled egg. Warm the milk, pour it slowly onto the yolks while whisking, then return it to a low heat and stir constantly. If it does scramble, a blender or a sieve rescues it.
Egg proteins set at around 70°C and milk boils at 100, so custard lives in a narrow band. Everything below is about keeping it there and never surprising the eggs with heat.
What you'll need
- Egg yolks
- Milk or cream
- Sugar
- Whisk
- Sieve (optional)
- Thermometer (optional)
Step by step
- Whisk the yolks and sugar together first.Until pale and slightly thickened. Sugar in contact with the yolks protects them from setting too quickly.
- Heat the milk to just below a simmer.Steaming, with bubbles at the edge, not boiling. Boiling milk poured onto yolks scrambles them instantly.
- Temper the eggs.Pour the hot milk onto the yolks in a thin stream while whisking constantly. This raises the egg temperature gradually. Doing it the other way round — eggs into hot milk — is how custard curdles.
- Return it to a low heat.The lowest that does anything. Patience here is the whole difference between custard and sweet scrambled egg.
- Stir constantly, reaching the corners.A wooden spoon or a spatula, in a figure of eight so nothing sits still on the base. The base is where it catches.
- Stop at coating consistency.It should coat the back of the spoon and hold a line when you draw a finger through. Around 80°C. It thickens more as it cools.
- Strain it into a cold bowl.Through a sieve, always — it catches any bits that did set, and stopping the cooking prevents it going further.
- Rescue it if it splits.Off the heat immediately, then a stick blender, or push it through a fine sieve. Both work well and nobody will know.
Tips
- A teaspoon of cornflour whisked in with the yolks makes custard far more forgiving — it can even be brought to a boil without splitting.
- Making it in a bowl over simmering water is slower and almost impossible to overheat. Worth it while you are learning.
- Custard thickens noticeably as it cools. Take it off slightly looser than you want it.
If it doesn't work
Lumpy or grainy
Cause: Overheated, so the eggs scrambled — Fix: Stick blender or a fine sieve. Next time use a lower heat and stir constantly.
Too thin
Cause: Not cooked to temperature, or not enough yolks — Fix: Return to a low heat and keep stirring until it coats the spoon. It also thickens on cooling.
Skin forms on top
Cause: Evaporation from the surface — Fix: Press cling film directly onto the surface while it cools.
Catches on the base
Cause: Heat too high, or not stirring the corners — Fix: Lower heat, and a spatula that reaches into the corners of the pan.
Questions people ask
How do I fix curdled custard?
Take it off the heat immediately and use a stick blender, or push it through a fine sieve. Both work, and the result is usually indistinguishable.
Why did my custard scramble?
The eggs got too hot too fast. Temper them by pouring hot milk onto the yolks while whisking, then cook on the lowest heat, stirring constantly.