In a large pot or steamer, add water and a steamer rack. The water should be at least 3-4cm below the steamer rack. Let the water heat and boil while you’re making the buns.
To make the bun wrapper, dust a surface and roll the dough a few times to make a ball. Divide it into two halves shaping each one into a long log shape. Cut into 5-7 pieces of dough. Roll these pieces in between your palms to make small bowls.
Then, one at a time, press the bowl into a round disc and using a rolling pin roll into a flat round sheet of 10cm diameter. Roll in such a way that edges are thinner than the center.
Drop a heaping tbsp of kimchi in the center of the rolled sheet. Start making the bun by lifting the edge on the side and keep on folding pr pleating it in between your thumb and forefinger until you reach the starting point. Seal the bun by twisting and pinching the folds in the center. Make sure it is secure and the filling isn’t leaking. Make rest of the buns in a similar manner.
Place a damp kitchen towel on the steaming rack and carefully transfer the buns there.
Maintain some distance between the buns because their size will increase a bit after steaming and they might stick.
Steam on high heat for 10-12 minutes.
Take the steamer rack out and transfer the bun out of the rack. Let them cool for 5 minutes.
Serve warm with soy sauce if desired.