Place dry shiitake mushrooms in a small bowl and cover with boiled water. Use something heavy on top (I used a whisky glass) to fully submerge your mushrooms. Leave them to soak for at least half an hour.
Squeeze mushrooms back over the bowl to remove and catch the excess liquid. Save this for later use. Then cut the mushrooms into thin strips (0.5cm or ¼ inch thick). De-stem any large stems.
Place into a small saucepan and add your mushroom liquid, vegan dashi and the rest of the ingredients. Bring to a simmer and make sure your sugar has dissolved
Add your sliced mushrooms and simmer for 20-25 minutes until the liquid has reduced by at least half. Allow to cool and store in an airtight container.
Notes
Use a small saucepan so the mushrooms sit properly submerged in the broth, this makes a big difference to the flavour.
I like to remove the stems for sushi as it gives a cleaner, more tender bite, but if you're just serving these over rice or in a bento, you can absolutely leave them on.
Don’t waste the leftover broth. It’s full of flavour and great as a quick marinade for tofu, or to toss into a simple vegetable stir fry.