Rinse the dried mushrooms briefly. You'll soak them later, but we're using the water they soak in, so you want them rinsed clean first.
Soak mushrooms in 300ml warm water.
Pan-fry or grill the pineapple on medium heat until browned on both sides. Don't use oil, though. Set pineapple aside.
In a pot, add soaked mushrooms and their liquid, then the cooked pineapple and the dried seaweed. Add another 700ml water (total 1 liter), 1 Tbsp coarse salt, and 5 tsp brown sugar. Stir to dissolve.
Bring to a boil, then reduce to low and simmer 40 minutes or until liquid is reduced to half its volume. (You can also boil it longer before simmering. In the video, it's simmering while covered.)
Let cool, then scoop out the big pieces before straining into a container.
Source:
https://www.youtube.com/watch?v=zoZmD2MVJY8