This is delicious as a spread for toast or scones, to sandwich together a sponge cake or as the filling for powder puffs. It keeps for weeks if well sealed and refrigerated after opening.
4 egg yolks
⅔ cup castor sugar
60g unsalted butter
2 tsp grated lemon zest
100ml lemon juice
Whisk egg yolks and sugar until well combined but not frothy.
Tip into a heavy-based non-reactive saucepan and add butter, zest and juice.
Stirring constantly, bring to simmering point over a medium-high heat (about five minutes).
As soon as bubbles appear, remove from heat, still stirring. Allow to cool.
Transfer to sterilised jars and seal.