• In a medium saucepan, warm the milk, stirring occasionally, over low-medium heat until it reaches 110℉.
• Remove from heat and stir in the yeast, sourdough starter, and sugar.
• To the bowl of a stand mixer fitted with the dough hook, combine the flour, salt, and milk mixture.
• Mix on low speed for 7 minutes. The dough should come together and appear well mixed and cohesive.
• Add the softened butter and continue to mix until completely combined. 
• Cover the bowl with plastic wrap or a damp towel and rest at room temperature for 1 hour.

Shape the Rolls

• Spray a 9x13" baking pan with cooking spray. Set aside.
• Divide the dough into 12 equal pieces weighing about 97 g each.
• Shape each dough piece into a ball by pulling opposite edges of the dough up to the top with your fingers. Pinch the dough to seal it. Do this several more times, rotating the dough until a smooth ball is formed.
• Place the dough balls into the prepared baking pan in a 3x4 formation, spacing evenly apart.
• Cover the baking pan with plastic wrap or a damp towel and let rise for another 30 minutes. The rolls will expand and nearly touch when done.
• While rolls are proofing, preheat oven to 375℉.
• Bake the rolls for 30-35 minutes until the tops are golden brown.