Prepare the levain and let it ripen for 12 to 14 hours.
Prepare the tangzhong by cooking flour and milk until thickened, then set aside to cool.
Mix the main dough ingredients including flour, tangzhong, milk, sugar, water, salt, and ripe levain.
Knead the dough until smooth and elastic.
Let the dough undergo bulk fermentation for about 3 ½ hours.
Divide the dough into portions, shape them into balls, and proof for 2 ½ hours.
Brush with egg wash, sprinkle sesame seeds, and bake at 450°F for 15 minutes, then reduce to 425°F and bake for another 5-10 minutes until well-colored.
Cool the baked buns on a rack before slicing.
