Heat the sesame oil in a large skillet over medium heat until hot. Add the spinach 3 to 4 cups at a time. Cook and stir to wilt, then add more spinach.
Grind the sesame seeds into fine crumbs using a mortar and pestle. When spinach is wilted, move it to the sides of the pan and sprinkle sugar in the center. When the sugar melts, stir in the spinach to coat.
Transfer spinach to a serving plate and sprinkle ground sesame seeds on top.
