Dissolve the sugar and yeast in the warm water for 5-10 minutes until frothy. Sift the flour into a mixing bowl, then gradually stir in the yeast mixture to make a firm dough. Knead for 5 minutes, then cover with a damp cloth and leave in a warm place to rise for 1-1 1/2 hours.
Knead the dough on a lightly floured surface for about 5 minutes, then roll into a long sausage. Cut into about 24 pieces and flatten each piece with the palm of your hand. With a rolling pin, roll out each piece into a circle about 4 inches in diameter.
Place a piece of wet cheesecloth on the rack of a steamer, arrange the buns 1 inches apart on the cheesecloth, cover and steam vigorously for 15-20 minutes. Serve hot.
I guess you can use waxpaper and cut them into squares for the bottom of the buns like they do in shops (instead of using cheesecloth), but I never tried it yet.