<human>: Goal: When rendering duck fat, what is the best way to cook it?

Which of the following methods is more reasonable for accomplishing this goal?

OPTIONS:
- Put duck fat in a pot and add vegetable stock over the fat. Simmer on low heat adding water as it evaporates for up to an hour. Remove and drain into jar.
- Put duck fat in a pot, pour about 3cm worth of water over the fat. Heat on medium heat. Once boiling drop the heat to low and simmer till yellow and murky.
<bot>: Put duck fat in a pot, pour about 3cm worth of water over the fat. Heat on medium heat. Once boiling drop the heat to low and simmer till yellow and murky.