I tried putting I think just milk and weed in a pot and letting it boil. Can't remember exactly what all we put in that :X

But it tastes like shit! I drank it all eventually, took a while to hit, then it was a pleasant body buzz for an hour or two. Don't have a clue how much I used (was probably a gram), and I'm pretty damn sure it was 2% milk. I know that you have to put the weed in the milk though, not in the water. Never heard of anyone using a double boiler for this, since it's usually better for things that will burn being cooked in just a hot pan (melting chocolate/etc).