Updated Jul 29, 2015Chatelaine
- FILL a canner with water, leaving a 2-in. headspace. Boil over high.
- BOIL plums with water, lemon juice, lemon zest and cardamom in a large pot. Reduce heat to medium and continue cooking, stirring often, until plums are soft and mixture is reduced to 6 cups, about 5 min. Scrape into a measuring cup to check, then return to pot. Stir in pectin until dissolved. Add sugar and bring to a rolling boil, stirring constantly. Boil hard for 1 min. Remove from heat and skim foam off surface.
- POUR into hot, clean Mason jars, leaving a 1/4-in. headspace at the top of each jar. Stir each jar with a non-metallic utensil to remove air bubbles. Wipe rim clean with damp paper towel, then cover with lid. Close with screw band.
- ADD jars to boiling water in canner, ensuring that they are covered by at least 2 in. of water. Bring to a rolling boil and process, covered, for 10 min. Turn off heat, remove canner lid and let stand, 5 min. Remove jars and cool. Check for seal after 24 hours. Lids should not flex up and down when centre is pressed. If they do, store in the fridge. Processed jars keep well up at room temperature for up to 1 year.