Ume-zing spiced plum jam

All the ume trees in our yard are producing plums like mad this year. We made ume-shu and with the remainder of the first harvest I cooked up this jam. It's really good. I'll be making some more because we're harvesting plums every other day now.

Ume-zing spiced plum jam
makes about 2 cups

1 kg ume
500 g sugar
1.5 tsp allspice
1 tsp cinnamon
1/2 tsp mace

1. Wash the ume and discard any with holes where bugs and birds have nibbled
2. Boil ume in a large pot until the skins split. Drain.
3. Add sugar and spices
4. Simmer until the sugar dissolves and pits are mostly separated from the flesh
5. Remove from heat and strain the pits and skins out
6. Bring the jam to about 100C, just boiling (it will set at 102C)
7. Transfer to sterile jars.

Consume with a month or so, or process the jars in the traditional canning method.