1 tbsp plus 1 tspactive dry yeast1½ cupswater, at room temperature4½ cupsbread flour6 tbspsugar3 tbspnon-fat dry milk powder1 tbspkosher saltRounded ½ tspbaking powder½ tspbaking soda1/3 cuprendered pork fat or vegetable shortening at room temperature, plus more for shaping the buns, as needed
Combine the yeast and water in the bowl of a stand mixer outfitted with the dough hook. Add the flour, sugar, milk powder, salt, baking powder, baking soda and fat and mix on the lowest speed possible, just above a stir, for 8-10 minutes. The dough should gather together into a neat, not-too-tacky ball on the hook. When it does, lightly oil a medium mixing bowl, put the dough in it, and cover the bowl with a dry kitchen towel. Put it in a turned-off oven with a pilot light or other warmish place and let rise until the dough doubles in bulk, about 1 hour 15 minutes.
Punch the dough down and turn it out onto a clean work surface. Using a bench scraper or a 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 25gm. Roll each piece into a ball. Cover the armada of little dough balls with a draping of plastic wrap and allow them to rest and rise for 30 minutes.
Meanwhile, cut out fifty 10cm squares of parchment paper. Coat a chopstick with whatever fat you’re working with.
Flatten one ball with the palm of your hand, then use a rolling pin to roll it out into a 10cm-long oval. Lay the greased chopstick across the middle of the oval and fold the oval over onto itself to form the bun shape. Withdraw the chopstick, leaving the bun folded, and put the bun on a square of parchment paper. Stick it back under the plastic wrap (or a dry kitchen towel) and form the rest of the buns. Let the buns rest for 30-45 minutes: they will rise a little.
Set up a steamer on 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 (reheat them for a minute or so in the steamer if necessary) or allow to cool completely, then seal in plastic freezer bags and freeze for up to a few months. Reheat frozen buns in a stovetop steamer for 2-3 minutes, until puffy, soft and warmed all the way through.