Curd Recipe Source: BakeWise Cookbook by Shirley O. Corriher. The recipe recommends using a double boiler. I tried the double boiler method and felt like it wasn't cooking the curd enough, the sugar was not dissolving, and it took a long time to thicken. So I took my chances and did the curd right on direct heat. If you are new to baking I would say try the double boiler method, it just takes longer (appr. 30 mins) to have the water boil, the curd cook, and the curd to thicken. If you feel pretty comfortable in the kitchen try the direct heat method. It's my personal preference. Curd can be stored in the fridge for up to 2 weeks. Regular lemons can be used as a substitute in this recipe!