With a sterilized spoon, take out the plums from the plum wine.
Measure the weight of the plums. It should be roughly 1.1 lb (500 g). Pour ¼ cup (60 ml) plum wine to a measuring cup.
Place the plums in a large pot and add water to cover the plums. Bring it to a boil and cook on medium low heat for 5 minutes.
Take out the plums and let cool until you can touch the plums.
Separate the flesh and seeds using a knife.
Mince the flesh. Measure the weight of the green plum flesh. You will need sugar that’s 50% of the weight of plum. My plums were 10.6 oz (300 g) total, so 5.3 oz (150 g) sugar.
Add the chopped plums, sugar, and plum wine in the saucepan.
Stir over low heat (simmer) until the sugar is dissolved, about 10-12 minutes. The jam should still be runny and it will thicken as it cools down.
Before transferring to the jars, increase the heat to high, and bring the mixture to a full rolling boil, stirring often. Transfer to hot sterile jars, leaving ¼ inch headspace, and seal. If the jam is going to be eaten right away, refrigerate. If you are going to keep it for a long time, process in a water bath, using a proper canning technique.
To Store
Store in the refrigerator for up to 2-3 weeks and enjoy it soon.
How to Sterilize the Jars.
I use my Instant Pot to sterilize jars and utensils. Instant Pot Ultra has "Sterilize" button, but if you use other Instant Pot models, you can select “Steam” program and set high pressure for 5 minutes.
Transfer the sterile jars onto a clean towel to cool.
Notes
Japanese Ingredient Substitution: If you want to look for substitutes for Japanese condiments and ingredients, click here.Recipe by Namiko Chen of Just One Cookbook. All images and content on this site are copyright protected. Please do not use my images without my permission. If you’d like to share this recipe on your site, please re-write the recipe in your own words and link to this post as the original source. Thank you.d link to this post as the original source. Thank you.