Chop mint leaves and stems.
Put mint and water into a saucepan and bring to a boil.
Turn down the heat and leave mixture for 10 minutes.
Strain the liquid back to the saucepan.
Add sugar and lemon juice and bring to a boil again.
Lower the heat and add wood-ear powder and stir the mixture well for 5 minutes. If the mixture is too thick, add an additional 50 ml of water.