Zest the lemons.

Add the zest and sugar to your mini food processor, blitz until zest is finely chopped and well incorporated in the sugar. Note: See post for details on skipping this step.

Juice your lemon(s), measuring out ⅓ cup of the juice.

In a small pot, whisk together egg yolks, large egg, and lemon sugar until well combined. Add the ⅓ cup of juice, whisk until well combined.

Cook over medium heat, whisking constantly, until mixture thickens. It should be able to coat the back of a spoon and retain a clear trail when a finger is dragged across the back of the spoon. Ideally, you want the mixture to reach 165F - I use a surface thermometer for this.

Once mixture is thick / hot enough, transfer to a bowl. Add the pieces of butter, whisking until well incorporated.

Once all of the butter has melted in and been fully incorporated into the curd, transfer to your storage container and chill for at least 1 hour before use.