Preheat oven to 240°F.
Spread cannabis trim on a parchment or foil-lined baking sheet. Bake in oven at 240°F for 25 to 30 minutes.
Melt butter or margarine in a heavy saucepan or double boiler. Add decarboxylated cannabis trim and stir. Add 2 cups water. Bring to a simmer over medium heat, then reduce heat to low, cover and continue to simmer for 2 hours.
Pour contents through a cheesecloth lined strainer into a large container. Press with rubber spatula to press liquids through.
Loosen up cannabis trim with a spoon, then pour boiling water over to flush butter through. Press firmly with rubber spatula to release all liquids.
Allow strained material to cool enough to put in the fridge. Refrigerate 2 hours or until butter hardens on top of liquid.
Separate butter from liquid and discard liquid.
Use cannabutter as you would regular butter or margarine.