2 heaping spoonfuls plum jam (about 1/4 cup, I think)
1-2 Tbsp soy sauce
1/2 tsp hot chili oil
1 tsp sesame oil
1/4 tsp freshly grated ginger
(1 tsp rice vinegar or sherry)
The plum jam I used was very sweet (compared to the stuff I used to get), so I added more soy sauce and some rice vinegar to cut the sugar. The soy and chili oil are the most important additions.
If the result is too thin, mix (maybe a teaspoon) cornstarch with enough water to make a paste, add that, and then cook the mixture till it bubbles a little. It should thicken upon cooling. (The plum jam will thin out when heated, so it ends up thinner when warm than before you added the cornstarch. Fear not.) You can make it all ahead of time and store in the refrigerator, so there’s time to make adjustments.