Stir together the yeast and 1 1/2 cups room temperature water in the bowl of a stand mixer fitted with a dough hook.

Add the flour, sugar, milk powder, salt, baking powder, baking soda and fat and mix on the lowest speed setting for 8 to 10 minutes. The dough should gather together into a ball on the hook.

Lightly oil a large bowl and put the dough in it, turning it over to coat it with the oil. Cover the bowl with a dry kitchen towel and put it in a warm place and let the dough rise until it doubles in size, about 1 hour 15 minutes.

Punch the dough down and turn it out onto a clean work surface. Using a sharp knife, divide the dough in half, then divide each half into 5 equal pieces. Gently roll the pieces into logs, then cut each log into 5 pieces, making 50 pieces total. They should be about the size of a Ping-Pong ball and weigh about 25 grams each. Roll each piece into a ball and set them on baking sheets. Cover them loosely with plastic wrap and let them rise for 30 minutes. While they're rising, cut out fifty 4-inch squares of parchment paper.

After 30 minutes, use a rolling pin to roll each ball into a 4-inch-long oval. Brush lightly with vegetable oil, lay a chopstick horizontally across the center of the oval and fold the oval over onto itself to form a bun. Gently pull out the chopstick, leaving the bun folded, and transfer it to a square of parchment paper. Put it back under the plastic wrap and form the rest of the buns. Let the buns rest for 30 to 45 minutes: they will rise a little.

Set up a steamer on top of the stove. Working in batches so you don’t crowd the steamer, steam the buns on the parchment squares for 10 minutes.

Remove the parchment. You can use the buns immediately or allow them to cool completely, then put them in plastic freezer bags and freeze for up to 2 months.

Reheat frozen buns in a stove top steamer for 2 to 3 minutes, until puffy, soft, and warmed all the way through. Freeze half the buns in airtight bags for another time.