Dissolve instant yeast and sugar in lukewarm milk.
Stir mixture until frothy.
In a stand mixer with a dough hook attachment, add the frothy mixture to the dumpling flour. Knead for 10 minutes.
Add cooking oil and knead for another 10 minutes.
Cover with a towel and let rest in a warm area for an hour.
Roll dough in a small amount of flour.
Cut in half.
Roll each half into a sausage formation.
Cut into 8 equal sized pieces.
Roll each piece into a thin circle (less than a 1/4 inch thick).
Flour each side and fold in half like a taco.
Place a small square of parchment paper on the bottom. This will prevent the bun sticking to the steamer.
Place dough in a steamer basket. ( I only did four in a basket so I didn't overcrowd them... they expand). If using bamboo baskets, you can stack up to 3 at a time.
Set steamer over ~1/2 to 1 inch of boiling water and let cook for 10 minutes. There is no need to flip them.