Wash the mugwort thoroughly and remove excess water.
Blend mugwort, coconut milk, erythritol, and salt until smooth.
Put the mugwort mixture and butter into a small saucepan. Stir and cook gently over low heat.
Once the mixture thickens, pour it into a square mold and spread evenly.
Let it set in the refrigerator for 1-2 hours, then cut into bite-sized pieces.