Add the butter, sugar, lemon juice, zest and cordial (if using) to a large pan and place over a low heat, stirring constantly until the mixture is smooth and the sugar and butter have melted.

Remove the pan from the heat and slowly pour the well-whisked eggs into the saucepan in a thin stream, whisking constantly as you add them (this agitation will stop the eggs from scrambling).

Turn the heat up a little and cook for 3 minutes or so until the mixture thickens up. It is really important you continue to stir the whole time, ensuring you reach all around the pan in order to stop the egg cooking too quickly; don’t let the curd boil!

The mixture is ready when it has thickened into a custard, turned opaque and coats the back of a spoon; pour into a clean sterilised jar and allow to cool to room temperature before popping in the fridge to set. A small piece of baking paper laid across the top of the curd will help prevent a skin forming.

The curd will last 2-3 weeks in the fridge or can be frozen for up to six months.