In a medium nonstick pan over medium heat, add the roasted black sesame seeds. Stir and do a quick toast for about 1 minute. Transfer to a plate to cool completely.
Ground the sesame seeds with a mini food processor (or grinder) into coarse powder. Transfer back to the plate. Set aside.
In a large pot or wok (with lid), put in the steaming rack and add water that reaches 1-inch below the top of the rack. Bring the water to a boil over medium heat.
Meanwhile, in a medium bowl, add the flour. Mix in the water and oil until combined. The dough should be almost like play dough, but runnier. Transfer the dough to a medium bowl that can be steamed and fit in the wok.
Put the bowl on top of the steaming rack. Cover the wok with a lid and steam for 20 minutes.
Once the dough is ready, carefully remove the bowl and place on a table. Have someone holding the bowl, stir the dough clockwise with a strong, long and thin utensil (like the handle of a wooden spoon) for 3 – 4 minutes. The dough will get stickier and tougher.
To make the dumplings, slightly grease a pair of chopsticks on one end. Holding the pair of chopsticks tightly, stab into the dough, pull out and twist the pair of chopsticks together to get approximately 1 tablespoon of dough. Now, take one chopstick in each hand. Scrap the chopsticks back and forth against each other, until the dough has moved to the end of a chopstick. Use a slightly greased hand to separate the dumpling from the chopstick. Roll the dumpling in the sesame seeds until the dumpling is completely covered. Place the dumpling on a small steaming plate. Repeat with the rest of the dough.
To serve, cover the dumplings (in the steaming plate) with aluminum foil. Re-steam the dumplings over medium heat for 6 – 7 minutes (make sure water is boiling before starting to steam). Serve immediately w/ a plate of sugar. Dip the dumplings in sugar to serve.