We call it plum nugget because of the golden nuggets of ginger floating in the ruby red jam. Yum. Our recipe for plum preserves can be hacked and reworked (walnuts instead of ginger?), but it's seriously amazing as is.
3 lbs firm-ripe red, black, or fresh prune plums, halved and pitted
3 cups sugar
2 oz port wine (we use a port from Argentina)
2 tbs crystallized ginger
juice of 1 lemon
In a preserving pan, combine the plum halves, sugar, and lemon juice. Bring to a simmer, and then pour into a bowl (ceramic is best). Cover the fruit with a sheet of parchment paper and refrigerate overnight.
Next day, separate plums from their juice. Bring this preparation to a boil in a preserving pan, stirring gently. Skim. Continue cooking on high heat 5 minutes, stirring constantly.
Place a candy thermometer in the jam. It will be ready when it reaches the setting point 105°C\220°F. Or eyeball it if you're a pro.
Add plums and return to a boil. Check the set or that the temp is back to 105°C\220°F. Do not let jam scorch.
Add the port and bring to a boil. Add the ginger and bring to a boil. Remove from heat.
Finish by filling the jars to within a 1/4 in of top with the preserves and seal (for jar preparation, see this detailed recipe). Boil for 10 minutes in a water bath. Let rest 5 minutes, then remove.
Makes about 4 to 5 8oz jars.