Dissolve yeast in 35°C water, add to flour and salt, mix with chopsticks until flaky, then knead into a dough. Cover with plastic wrap and let it rest for 15 minutes.
Grind pork if not already minced. Mix with all seasonings except sesame oil, adding water in 2-3 increments. Blanch shepherd's purse, cool in water, drain, chop, and mix into pork filling. Add extra salt if needed, then blend in sesame oil.
Cut the rested dough into equal portions and flatten each.
Roll out each piece into a circle with a thicker center and thinner edges.
Place an appropriate amount of filling on each dough circle.
Fold and shape into buns.
Place the buns in a steamer, let them rise for about 1 hour, then steam on high heat for 20 minutes. Turn off the heat and wait for 3 minutes before uncovering.