Lemon curd is a bright, tart layer that cuts through sweet cream and sponge. The most common failure is an eggy taste or little scrambled bits. The cause is overheating, when the yolks set on their own instead of thickening the liquid.
Ingredients and what each one does
- Lemon, juice and zest. The juice brings acid, the zest brings aromatic oils, without which the flavour is flat.
- Sugar balances the acid and supports the structure.
- Eggs thicken it: protein sets as it heats and holds the liquid.
- Butter adds smoothness and gloss and softens the acid.
How to make it
- Zest the lemons before juicing. Rub the zest into the sugar: the sugar draws out the oils and carries the aroma.
- Combine the sugar and zest with the juice and eggs in a heatproof bowl or pan.
- Cook on low heat or over a water bath, whisking constantly. Do not boil. Eggs set at about 70 °C, and boiling gives lumps.
- Cook until thick, about 75 to 80 °C. Sign: it coats the back of a spoon, and a line drawn with a finger stays. This usually takes 8 to 12 minutes.
- Off the heat, whisk in the butter piece by piece until melted.
- Strain through a sieve to remove zest and any small lumps. Cover with film touching the surface and chill. It thickens more as it cools.
What can go wrong
- Eggy taste, lumps. Overheated. Strain it, and heat more slowly next time.
- Runny. It did not reach 75 to 80 °C. Return it to the heat for a few minutes.
- Metallic taste. It was cooked in aluminium: acid reacts with the metal. Use stainless steel or a glass bowl.
- Too sour. Add more sugar or use less juice.
Substitutions
Lime or orange work too. Orange is much milder, so use less sugar. Yolks only, instead of whole eggs, give a richer colour and a thicker texture.
Storage
In the fridge under film for 1 to 2 weeks. It can be frozen.
