We like yellow potatoes best here, but you can buy baby potatoes of any color that are ¾ to 1 inch in diameter. If you can only find larger baby potatoes, cut them into 1-inch pieces.
Whisk ⅔ cup water, soy sauce, and corn syrup together in small bowl. Set sauce aside.
Add potatoes and salt to 14-inch flat-bottomed wok or 12-inch nonstick skillet and cover with water by 1 inch. Bring to boil and cook for 5 minutes. Drain and pat dry with paper towels. Wipe wok dry with paper towels.
Heat oil in wok over medium heat until shimmering. Add potatoes and cook, tossing occasionally, until nearly tender, about 8 minutes. Add sauce, toss to coat potatoes, and bring to simmer. Cover and cook for 1 minute. Uncover and continue to cook, tossing occasionally, until potatoes are fully tender and well seasoned, about 6 minutes.
Increase heat to medium-high and add sugar. Cook, tossing constantly, until sauce becomes thick and stringy, about 4 minutes. Remove from heat and stir in sesame seeds, green onion, and gochugaru. Serve. (Refrigerate for up to 4 days.)
