Chop the celery finely and squeeze the extra juice out. Mix with other ingredients for the filling and stir until all the ingredients well combined. Set aside.
Combine all the ingredients for the dough and mix until dough forms. Knead the dough until smooth. Cover with plastic wrap and let stand 60 minutes until the dough double in size.
Punch the dough down to release gases. Divide dough into 10-12 equal portions, each is about 30-40 grams and let stand for 10 minutes. Roll each dough on lightly floured surface into a circle, 13-15 cm in diameter. The center of the circle should be thicker than the edge. Place one portion of the prepared filling in the center of each dough circle. Wrap the dough to enclose the filling. Pinch edges to form the bun.
Cut waxed paper into 10-12 squares and brush one side of paper lightly with oil. Place a bun, seam side down, on each square. Let the buns stand for 30 minutes.
Bring a pot of water to boil and steam the buns over the medium heat for 18 minutes.