Sigh, more plums. The lady who lived here, who planted all of the trees around for a half a mile, must have liked plums. In her memory I’ll get on the plum wagon.
2 lbs greengages (about a kilo)
water, enough to just cover the fruit in the pan
1.5 - 2 lbs sugar, or to taste (700g-1 kilo)
the juice of half a lemon
large, heavy-bottomed pan
ladle or funnel
This made these three jars of jam.
My mother-in-law was pressed into service once more; we cut the greengages in two to remove their stones/pits. Apparently, like the damson, they have a seed within that can be used to flavor jam that you make with them. We just boiled them down to jam consistency with the juice of half a lemon. As usual, I used less sugar than others--as the pulp cooks down, just add as much as sugar as makes it taste acceptable to you, though the usual pound of sugar per pound of pulp rule seems to apply as per the relevant jam literature.
As the pulp cooks down, you'll be able to tell when you've reached the magical setting moment--the liquid won't run off of a spoon, but will glop. If you're in any doubt, drop a dollop onto a plate that's been in the freezer for ten minutes--if the jam wrinkles when you push it with your finger, it's done. Greengages, as they are little plums, are high in pectin and don't need any help beyond cooking to do this. When the moment has come, ladle the jam into sterlized jars, pop on the lids, and allow to cool.*
*To sterilize jars, wash jars and lids in soapy water. Sterlise the lids by dipping them in boiling water and allowing them to air dry. Sterlise the jars by placing them (opening up) on a cookie sheet covered in paper towels, and allowing to dry in an oven set to 160°C / 320°F. See here and here for more information on preserving.