Rinse the sweet potatoes well, slice into rounds, then soak in water. If you skip this step, the color will not turn bright.
Add all of the ingredients to a sauce pan, bring to a boil on high heat, then simmer for about 10 minutes on low heat. Cover with a drop lid to prevent the potato slices from breaking apart while simmering.
When a skewer goes all the way through the sweet potatoes, remove the gardenia seed, and then it's ready to serve. They are delicious served either hot or cold. When serving cold, let them cool in the stewed liquid.
Enjoy them either hot or cold.