1. 1. Activate the Sourdough and Prepare the Dough Base: In a large mixing bowl, combine the active sourdough starter, warm milk, 1/4 cup granulated sugar, melted butter, egg, and vanilla extract. Whisk these wet ingredients together until well combined. Gradually add 2 cups of the all-purpose flour and the salt, mixing until a shaggy dough forms.

2. 2. Knead the Dough and Begin the First Rise: Add the remaining 2 cups of flour, one cup at a time, mixing until the dough comes together. Turn the dough out onto a lightly floured surface and knead for 5-7 minutes until it’s smooth and elastic. Place the dough in a lightly oiled bowl, turning once to coat. Cover the bowl with plastic wrap or a clean kitchen towel and let it rise in a warm place for 2-4 hours, or until doubled in size. Alternatively, you can refrigerate the dough overnight for a slower, more flavorful rise.

3. 3. Prepare the Filling Ingredients: While the dough is rising, prepare your filling. In a medium bowl, combine the softened 1/2 cup unsalted butter, brown sugar, and ground cinnamon. Mix until it forms a smooth, spreadable paste. Set aside. Ensure your diced peaches are ready to go.

4. 4. Assemble the Rolls: Once the dough has doubled, gently punch it down and turn it out onto a lightly floured surface. Roll the dough into a large rectangle, approximately 18×12 inches. Spread the cinnamon-sugar butter mixture evenly over the entire surface of the dough, leaving a small border along one of the long edges. Sprinkle the diced peaches over the butter mixture.

5. 5. Roll and Slice the Dough: Starting from the long edge opposite the clean border, carefully roll the dough tightly into a log. Once rolled, use a sharp knife or unflavored dental floss to cut the log into 12 even slices, about 1.5 inches thick.

6. 6. Second Rise and Baking: Arrange the sliced rolls in a greased 9×13 inch baking dish, leaving a little space between each roll. Cover the dish loosely with plastic wrap or a kitchen towel and let the rolls rise again in a warm place for another 30-45 minutes, or until they look puffy. Preheat your oven to 375 F (190 C). Bake for 25-30 minutes, or until the rolls are golden brown and cooked through.

7. 7. Whip Up the Cream Cheese Frosting: While the rolls are baking, prepare the frosting. In a medium bowl, beat together the softened cream cheese and 1/4 cup softened butter until smooth and creamy. Gradually add the powdered sugar, mixing until fully incorporated. Stir in the vanilla extract and 2 tablespoons of milk or heavy cream, adding more milk a teaspoon at a time if needed, until the frosting reaches a smooth, spreadable consistency.

8. 8. Frost and Serve: Once the cinnamon rolls are out of the oven, let them cool for about 5-10 minutes. Spread the cream cheese frosting generously over the warm rolls. The warmth of the rolls will slightly melt the frosting, allowing it to seep into all the nooks and crannies. Serve immediately and enjoy!