Mix dough ingredients. In a large mixing bowl add the milk, sugar, salt, butter, and the active sourdough starter. Using a bread whisk or whisk, stir to combine. Once the ingredients are well combined add in 1 cup of the bread flour. Stir to combine. Then add in the rest of the bread flour. Stir to combine.
Brief rest. Once combined, allow the dough to sit covered for 30 minutes. Keep in mind the dough will be pretty sticky. This is the correct texture of the dough.
First stretch and fold. Wet your hands with water (to prevent the dough from sticking to your hands) and grab one section of the dough. Stretch the dough out and fold it over. Turn the bowl by ⅓ and repeat this process. Turn ⅓ and repeat. Flip the dough over so the bottom is facing the top. Cover the bowl and allow it to sit for 30 more minutes.
More stretch and folds. Repeat the stretch and folds process 2 more times for a total of 3 stretch and folds sessions.
First rise. After the 3 stretch and folds, allow the dough to rise for 10-16 hours. Overnight is best. Keep in mind that the rise time can vary depending on the temperature of your kitchen.
Shape. Grease a 9x13 casserole dish with some baking spray. Using the all-purpose flour, dust your working surface and turn the dough out onto the floured surface. Separate the dough into 12 equal parts and shape them into balls. You will want to use some of the all-purpose flour to help prevent the dough from sticking to your hands.
Second Rise. Place the dough into the prepared baking dish. Brush the top of the rolls with some egg wash, cover, and allow to rise for 30 minutes to 1 hour in a warm place
Bake. Preheat the oven to 375 degrees. Bake rolls at 375 degrees F for 30 minutes or until golden brown. Remove from the oven and allow to cool for 20 minutes before serving.