In a medium pot, bring 4 cups water to a boil. Once boiling, add the dried resinous polypore, then cover and reduce heat to maintain a simmer. Simmer for 45 minutes.
Set a strainer over a bowl and strain out the liquid. You should have about 1 ½ to 2 cups of mushroom broth. Set the mushroom broth aside.
(optional) Use a potato ricer to squeeze extra liquid out of the leftover mushrooms.
Note: for a stronger mushroom flavor in the syrup, simmer down the strained mushroom broth, uncovered, until its volume has been reduced to about ⅓.
Strip the rosemary leaves from the stems and bruise them with a knife to help release their flavors. Place the rosemary leaves, thyme, hibiscus, and sugar in a heat-proof sterile quart jar.
Bring the remaining 2 ½ cups of water to just shy of a boil, then pour into the jar with the herbs. Give it a good stir, then cover the jar and let steep for about 45 minutes.
Place a strainer over another sterile quart jar, and strain the rosemary syrup into the second jar.
Add the lemon juice and ½ cup of your mushroom broth, to obtain 1 quart of the syrup.
To serve, place a few ice cubes in a glass, then pour in about 1 part syrup-broth mixture to 4 parts bubbly water. Give it a quick stir, then taste. Add more syrup or bubbly water as desired. Enjoy!
Extra syrup can be frozen.