1. In a large mixing bowl, combine your active sourdough starter, warm milk, granulated sugar, egg, melted butter, and vanilla extract. Whisk these wet ingredients together until well combined. Gradually add the all-purpose flour and salt, mixing with a wooden spoon or your hands until a shaggy dough forms.

2. Turn the dough out onto a lightly floured surface. Knead for 8-10 minutes until the dough is smooth, elastic, and no longer sticky. It should spring back slowly when you gently press it. Place the kneaded dough into a lightly oiled bowl, turning it once to coat, then cover with plastic wrap or a clean kitchen towel.

3. Let the dough rise in a warm place for 2-4 hours, or until it has nearly doubled in size. The exact time will depend on the strength of your sourdough starter and the temperature of your kitchen. This slow rise develops the characteristic sourdough flavor.

4. While the dough is proofing, prepare your filling. In a medium bowl, combine the finely diced fresh strawberries, packed brown sugar, softened unsalted butter, and 1 tablespoon of all-purpose flour. Mix everything together until the strawberries are evenly coated.

5. Once the dough has proofed, gently punch it down and turn it out onto a lightly floured surface. Roll the dough into a large rectangle, approximately 12×18 inches. Spread the strawberry filling evenly over the entire surface of the dough, leaving a small border along one of the longer edges. Starting from the opposite long edge, tightly roll the dough into a log.

6. Using a sharp knife or a piece of unflavored dental floss, slice the log into 12 even pieces, about 1.5 inches thick. Arrange the sliced rolls in a lightly greased 9×13 inch baking dish, leaving a little space between each roll. Cover the dish loosely with plastic wrap or a kitchen towel.

7. Let the rolls proof again in a warm place for another 30-60 minutes, or until they look puffy and have nearly touched each other. Preheat your oven to 375 F (190 C) during the last 15 minutes of this proof. Bake for 25-30 minutes, or until the rolls are golden brown on top and cooked through.

8. While the rolls are baking, whisk together the powdered sugar, 2-3 tablespoons of milk or cream, and 1/2 teaspoon of vanilla extract in a small bowl until smooth and pourable. Once the rolls are out of the oven, let them cool for about 5-10 minutes in the pan, then drizzle generously with the prepared glaze. Serve warm and enjoy!