Felicity Cloake has just published an article on the perfect lemon curd which can be used for any sharp fruit such as grapefruit, blackcurrants etc. Perfect lemon curd:
(Makes 400ml)
5 unwaxed lemons
225g white sugar
6 eggs (3 whole eggs and 3 yolks)
Pinch of salt
100g butter, cubed
Zest three of the lemons into a bowl with the sugar and rub together with your fingertips to release the oils, then squeeze enough of them to give 225ml juice.
Whisk the eggs into the sugar followed by the lemon juice, a little at a time, until fully incorporated.
Put in a heavy-based pan over a low heat and stir continuously with a rubber whisk or wooden spoon until as thick as Bird’s custard which should take about 7-8 minutes. Whisk in the salt and pour into a food processor or blender if you have one. Cool for five minutes.
Start the motor and blend on a low speed for 30 seconds (alternatively, beat with a wooden spoon), then start dropping in the butter, a little at a time, still with the motor on, until smooth. Transfer to sterilised jars where it will last upto a week.