Prep (for both methods)

1. Fill a medium bowl with water and add 1% salt (e.g., 10 g salt per 1 L water).
2. Cut sweet potato into 1-inch wedges using the rangiri technique. Hold your knife at an angle, make a diagonal cut, then roll the sweet potato a quarter turn before making the next diagonal cut. Repeat until the whole potato is cut—this creates evenly sized, faceted pieces that cook more quickly and evenly.
3. Soak the pieces in salted water for 10–15 minutes.
4. Drain and pat dry thoroughly with paper towels.

Deep Fried Method

1. Place the sweet potatoes into a wide pot. Add enough neutral oil to cover the potatoes completely.
2. Turn heat to medium and bring oil up to 160–170°C. Fry potatoes for 10–15 minutes, or until a skewer pierces through with little resistance.
3. Increase heat to 190°C and fry for about 1-1.5 more minutes until golden and crisp. Remove and drain on a wire rack or paper towel.
4. In a clean pan, combine sugar, mirin, water and rice vinegar (if using) and stir with a spatula. Place on to burner over medium and heat until large, slow bubbles begin to form. If you have a infrared thermometer or candy thermometer, heat until it reached 300-310 F or until you can draw a line on the pan with the spatula. Drizzle in the soy sauce and then add fried sweet potatoes. Turn off the heat and toss until coated evenly in the syrup. Sprinkle with sesame seeds. 
5. Transfer to parchment-lined tray/plate, separating pieces so they don’t stick. Enjoy!!

Pan Fried Method

1. In a pan, mix oil, sugar, rice vinegar (if using) and soy sauce. Add the sweet potatoes. Cover with a lid thats been wrapped with a towel* and set over medium heat.
2. Once it begins bubbling, swirl the pan, then reduce heat between low to medium-low. Cook undisturbed for 6-8 minutes.
3. Remove the lid (wipe off any excess water from the steam if using a lid without towel wrapped). Flip potatoes and add butter in 3 different spots of the pan Cover again and cook for another 4-5 minutes or until tender. 
4. Remove lid, tilt pan to spread melted butter, and cook uncovered for 2–3 minutes until golden and lightly crisp.
5. Quickly transfer to a parchment-lined tray/plate. Optionally, drizzle with any remaining syrup from the pan. Sprinkle with sesame seeds and enjoy!