Preheat oven to 240°F. Place the cannabis on your baking sheet and spread evenly. If you have large flowers, break them by hand to smaller chunks.
Cover with parchment and place in oven for 35-45 minutes. Be sure to mix (or just shake the pan) every 10 minutes while it bakes.
Grind the cannabis to a medium/fine course. It's ok to use entire plant, just the flower, a little bit of both — this is all a matter of preference. Anything small enough to fit through the strainer will end up in your product so be careful grinding.
Melt the butter. Add 1 cup of water and 2 cup of butter into a stock pot or saucepan. Simmer on low and let the butter melt. Water regulates temperature to prevent burning.
Add cannabis and simmer. Once melted, add in your coarsely ground cannabis product. Maintain low heat (between 160ºF and - never exceeding - 200ºF) and let the mixture simmer for 2 to 3 hours, stirring occasionally. Do not boil.
Strain and store the butter. Set the funnel on top of a jar and line it with cheesecloth. Pour the butter (once cooled) over the cheesecloth funnel and allow it to strain freely.