In a medium saucepan on very low heat, add water and butter or ghee.
When the butter is melted, add the decarboxylated cannabis. Mix well with a wooden spoon and cover with lid. Let mixture gently simmer for 2-4 hours. Stir every half hour to make sure your butter isn’t burning. Maintain low heat (ideally above 160ºF but never exceeding 200ºF). The mixture should never come to a full boil.
Place cheesecloth in funnel and allow weed butter to strain freely into a mason jar. Let the butter cool to room temperature. Use immediately or keep in refrigerator or freezer in a well-sealed mason jar for up to six months.