Lemon curd is easy to can at home in a simple water bath canner. It's perfect for edible holiday gifts. This recipe also works with lime curd.
Prepare a water bath canner and bring it to 180 degrees. Hold it at that temperature (not boiling) while you prepare the lemon curd for canning.
Start water simmering in the bottom of a double boiler.
In the top bowl of the double boiler, off the heat, whisk the egg yolks and whole eggs. Add in the sugar and zest and whisk thoroughly. Finally, add in the lemon juice and chunks of cold butter.
Place the bowl on top of the double boiler and heat while whisking constantly. Once the mixture reaches 170 degrees, remove from heat and continue whisking for another 5 minutes while the mixture thickens.
Pour the lemon curd into prepared half-pint canning jars, leaving 1/2 inch headspace. Center canning lids and seal to finger tight.
Place the jars in the water bath canner and slowly bring it up from 180 degrees to boiling. This should take 25 to 30 minutes. Boil the mixture for 15 minutes and then turn off the heat. Leave the jars in the canner for 5 more minutes before removing them.
Allow the jars to cool to room temperature before checking seals. Store any unsealed jars in the refrigerator or freezer. Sealed jars will keep for 3-4 months.
The recipe and process are the same for lime curd and key lime curd, with one difference. Reduce the total amount of zest from 1/2 cup to 1/4 cup. Lime zest is a bit more intense and you don't need quite as much. Otherwise, just substitute lime juice for lemon juice and proceed with the recipe. Recipe yields 3-4 half pints.