Buns From Starter

Combine the sourdough starter, milk, and bread flour and scrape the bowl. Knead until smooth. Cover and let dough sit for 30 minutes.

Combine the remaining flour, cornstarch, dough conditioner if using, salt, and sugar, then add to the mixer bowl a little at a time.

After everything is incorporated, knead all the ingredients for about 3 minutes to make a sticky, cohesive dough.

Stop the mixer and use a wet spatula to scrape the bowl.

Add the butter across the top.

Slowly turn the mixer to medium and then high and continue to knead until the dough is smooth and elastic, about 12 minutes.

Use a wet spatula to scrape the dough hook and bowl.

Cover the dough and let it rest in a warm place for about 2 hours, until puffy. Don't expect it to actually rise much.

Use cooking spray to grease the wells of hamburger bun pans.

Oil your work surface, your dough blade, your scale, and your hands. Turn the dough out onto the work surface, divide it into 12 equal pieces about 4-4 1/2 oz. each, and put them in the wells of the pan.

Going back to the first dough ball, pull each out on to the work surface. Stretch and fold a few times, until the dough forms a fairly smooth ball (it will still be loose and floppy). Put the ball back into the well and move on to the next.

Spritz with water and let them rise until puffy and rounded, about 1 1/2-2 hours in a warm place.

When the rolls are nearly ready, heat the oven to 350°F. Brush the buns with the beaten egg yolk/water mixture. Sprinkle with toppings.

Bake the buns for 25-30 minutes, or until golden brown.

Remove the buns from the oven to a cooling rack and allow them to cool before serving.

Store buns at room temperature for two days; freeze for longer storage.