First, wash your sweet potato with clean water and cut it into 2cm long chunks. Soak in water and microwave for 4-5 mins until soft.
Grab a frying pan and add the sesame oil, the sugar, the soy sauce and the vinegar. Simmer on low heat for about 30 seconds until the sugar dissolves.
Add the sweet potato chunks and let them cook for about 2 minutes on each side until crispy.
Once the chunks have caramelised, remove from the heat and sprinkle with the black sesame seeds. Serve warm or room temperature.