Add milk, oil, and starter to a stand mixer with a paddle or dough hook. Mix on low until the starter is dissolved. Then add an egg and mix on low.
In a small bowl, mix together salt and sugar. Add this mixture to your flour and mix until well incorporated. Then add the flour mixture to the stand mixer and mix on low until incorporated. NOTE: I added about 1/3 C of additional flour because my dough was very sticky. I added flour until it looked soft, but not overly sticky.
Oil a medium sized bowl, and place your dough in it. Or you can remove the dough from the stand mixer bowl, clean it, oil it, and place the dough back in it. Make sure to get oil on both sides of the dough, then cover it with plastic wrap and allow to ferment for 4-6 hours.
Remove the dough from the bowl and place it on your counter. Roll the dough into a log. With a bench scraper, cut your dough into the desired sizes. Roll the dough into a ball and place on a pan lined with parchment paper.
Lightly press your palm on top of the dough, flattening the ball until it's about 1 inch tall. Lightly cover with a towel or oiled plastic wrap and allow to rest for 30 minutes.
Brush each bun with the egg wash and sprinkle the top with sesame seeds. Bake at 400 degrees for 15 minutes until golden brown.