Full disclosure: I didn’t come up with this idea, but stumbled across this blog post a while ago and have been using this method ever since. This time I took note of quantities and times, in case someone is interested in trying. I used 14 blocks of Westgold unsalted butter (bought in Woolies) and it took 1 hour and 35 minutes in the low setting of my slow cooker for all of them to melt.
What I do next is to ladle the ghee into jars through a sieve lined up with cheesecloth. The finer the sieve (or the more layers of cheesecloth you use), the better, but the more patient you need to be.
How do you know you should stop pouring melted ghee into your jars? In theory, if you have a good enough straining device you should be able to pour everything because it would get filtered anyway. In practice, I always stop when I start getting more than a few drops of milk solids in every spoonful I take.
I always use the last jar first, because it’s the one that has more milk solids and therefore will last less. In theory pure ghee should be shelf stable for months, but I prefer to play it safe and keep my jars in the fridge.