Cut each yuzu in half crosswise, squeeze out the juice, and remove the seeds. I yielded 250 ml of juice out of 2 kg of yuzu.
Scoop out the insides of the peels, and discard. Keep the peels.
Cut the peels in half, then thinly slice them.
Put sliced peels into a pot with plenty of water, bring to a boil, then drain. Repeat this twice.
Combine the peels from Step 4 and the yuzu juice from Step 1 in a pot, add the grated apple into it, add the sugar, then heat it up.
Simmer on low to medium heat for about 30 minutes while stirring and removing the scum.
It will harden after cooling down, so it is ready when it is still slightly runny. Store in a jar or vinyl bag and keep it in the refrigerator.
Dissolve a generous spoonful in hot water and drink up.
Story Behind this Recipe
I receive a ton of yuzu every year. Ever since my mother-in-law taught me how to make yuzu jam, I've been making it every year. I am sharing the recipe here to keep as a record.
Keep an eye on the pot while it is boiling, and to prevent burning, stir it up from the bottom. While boiling, the yuzu jam may sputter out, so be careful. The photo shows 3 times the amount (6 kg) of yuzu. I make a bunch and freeze it.