Start the night before by mixing the ingredients for the dough. Melt the butter in a small sauce pan. Mix the flour, starter, sugar, milk, egg, baking powder, butter, and salt.
While the dough is mixing with the dough hook in the Kitchen-Aid mixer, the consistency of the sourdough sweet rolls will be a firm dough that is not sticky. After the dough comes together in a ball, it will sit overnight until I'm ready to make the sweet rolls. In this case, I mixed the dough around 11pm and put the remaining ingredients in the rolls around 2pm the next day. The dough is very flexible. I have made these rolls after an 8 hour fermentation or have waited as long as 15 hours.
Cover the dough in a bowl and allow it to sit on the counter overnight.
Begin making the blueberry sauce for the filling. In a small sauce pan, add the blueberries, sugar, and flour. Heat the blueberry mixture, stirring often, until the blueberries, sugar, and flour have become a sauce like mixture.
Lightly flour the counter and roll out the dough intona rectangular shape, measuring about 18 inches by 10 inches.
Spread the blueberry sauce evenly over the dough.
Roll the dough starting at the long side of the dough. As you are rolling, try to keep as much of the blueberry filling in between the layers of the rolls.
Then, cut the rolls using an unwaxed and unscented floss. I like this silk floss. Start by cutting the rolls in half. Then, each half will be cut in half until you have 16 cut rolls.
Place the cut rolls in a 9x13 pan and topp evenly with the remaining 1/2 cup of milk. Cover the allow to rise in a warm place for about an hour.
Preheat the oven to 350F. I like to place the rolls on the back of the stove top so that as the oven is preheating, the rolls are in a warm spot to rise.
Bake the rolls for 35 minutes or until the tops of the rolls are lightly brown and the middle rolls don't appear soggy.
While the rolls are baking, prepare the lemon glaze.
Mix the juice, zest, and sugar together well so there are no lumps from the sugar and set aside.
After removing the sweet rolls from the oven, allow them to cool for 5 minutes before topping with the lemon glaze. Then, evenly pour the glaze over the sweet rolls. Allow the sweet rolls to cool for another 5 minutes, then serve.