You need a good sharp grater, one that allows you to use just enough pressure to remove only the lemons’ outermost zest. Anything below the first fine layer of zest will be bitter rather than pleasantly sour and take your curd well beyond lip-puckering. The zest should be so fine as to be indefinable in the finished preserve – this isn’t marmalade.
If you can wait, leave rock-hard lemons you just bought till they are soft enough to dent with your thumb. You will get much more juice. The warmer the fruit, the more juice they will give. I leave mine in the warmth of the kitchen, or put them in the bottom of the oven for 10 minutes before I squeeze them. Failing that, a good firm rolling on the table with the palm of your hand will do the trick.
Most lemon curd recipes instruct you to stir the mixture with a wooden spoon. I find that stirring lightly with a whisk introduces just a little more lightness into the curd, making it slightly less solid and more wobbly.
- zest and juice of 8 unwaxed lemons – or fewer – all together you are aiming at about 600 ml yellow substance. We successfuly produced lemon curd with help of the juice only (no zest), when fresh lemons were in short supply. In such case we need 400 ml of juice only, to match the balance of sugar, eggs and butter below,
- 400g sugar.
- 200g butter.
- 6 eggs and 2 egg yolks.
- Put the lemon zest and juice, the sugar and the butter, cut into cubes, into a heatproof bowl set over a pan of simmering water, making sure that the bottom of the basin doesn’t touch the water.
- Stir with a whisk from time to time until the butter has almost melted.
- Mix the eggs and egg yolk lightly with a fork, then, when butter almost gone, stir eggs into the lemon mixture.
- Let the curd cook, stirring regularly, for about 10 minutes, until it is thick and custard-like. It should feel heavy on the whisk, but still runny.. It will set when cold.
- Remove from the heat and stir occasionally as it cools.
- Pour into spotlessly clean jars and seal.
It will keep for a couple of weeks in the refrigerator.