Make leavening: add flour and water and make a soft dough, leave to ferment at room temperature for about 24 hours to form leavening;

And noodles: add flour and water to the fermented leavening, and form a dough, and leave to rise at room temperature for about 24 hours;

Make steamed buns: wake up with a very soft and sour dough, add lye, and add a little bit of lye after you smell it is not sour. Knead into the flour until it feels harder to the touch. Roll out the dough, roll into a long square piece, sprinkle with flour, triple fold and repeat eight times. Roll out into a long square, roll up, and brush with water to prevent cracking. Cut into rectangular buns, wake up for 45 minutes;

steaming: boil water, arrange buns into the pot. Timer on steam, 15 minutes on high heat.