Peel the sweet potato and slice into 1/2"-thick rounds.
Heat the oil in a medium-sized saucepan; when it's hot, add the brown sugar to the oil. I know it's weird - but it works :).
When the brown sugar floats, add the slice sweet potato and fry about 10 minutes, turning every once in a while to get the brown sugar all over the potato.
When the potato is tender, remove from pan and let it cool off a few minutes - that sugar is HOT.
You can serve this on a plate, or on a bamboo skewer.