Take the butter out of the fridge and let it come to room temperature - about 15-20 minutes. Cut it into small cubes.
Heat a kadai. Melt the butter cubes completely on a low-medium flame.
Soon, the butter will start boiling with bubbles and will begin to froth and rise. At this point, turn the heat to low and let the butter continue to simmer. The color will change to a dull brown.
Add the salt along with the curry leaves or drumstick leaves now. Turn off the gas. To check if the ghee is ready, add a few drops of water - it should splutter in the ghee.
Pour the ghee into a jar, avoiding the residue at the bottom. You can see that the ghee will be dark brown and will turn yellow by the next day.