Wash the sweet potatoes and cut into chunks. Soak in water, then drain with a strainer.
Line a frying pan with paper. Add the vegetable oil, potatoes, and sugar. Cover with a lid and heat on medium.
When the lid becomes hot, use chopsticks to stir. Cook for 10～20 minutes on medium-low heat.
Cooking time depends on how you cut the potatoes. They are ready when you can easily push a chopstick or skewer through.
Toss with sesame seeds and serve on a plate.
When opening the lid, wipe off the condensed water.
Story Behind this Recipe
This is the recipe I've been using for 15 years.
Water will collect on the lid, so wipe it off when you remove it. When cooled, the surface will harden like candy. (If it is a hot day, chill in the refrigerator). If you eat the potatoes while hot, you will burn yourself, so be careful.