While any plum will do in this recipe, Green Gage Plums add the perfect sweetness.
Wash and cut the plums into quarters, discarding the pit. Leave the skin on. Slice plums roughly into a small, heavy saucepan. Add water and bring to a boil over medium heat.
Once it boils, add sugar, salt, ginger, black pepper and vanilla (if using). Cook for another 7-10 minutes, uncovered, and stir occasionally. Adjust heat so it doesn't boil over. The consistency will be like liquid jelly.
Remove from heat and cool to room temperature.
Process in your canner as you would a jam, or enjoy on its own or with almost anything you want to pair it with, from spreading it over a piece of sourdough toast to mixing it with rice at the end of the meal.