Depends on how much oil you want to make (or butter). If you're really committed to some eating, here's the recipe I use:

http://boards.cannabis.com/recipes/8...-brownies.html

That's a lot of bud, but it makes a lot of oil. I like to make a whole bottle at a time, so I only have to make it every few months, because it's kinda stinky cooking it down and makes the whole house reek.