01 -
In a large bowl, whisk together the active sourdough starter and milk until fully dissolved. Whisk in the sugar and egg. Add bread flour, salt, and room temperature butter. Mix by hand until butter is fully incorporated. Let the dough rest for 30 minutes covered with a damp cloth. Perform two sets of stretch and folds, allowing the dough to rest between each session, or knead in a stand mixer on medium speed with a dough hook for 12 minutes. Cover with a damp cloth and let the dough ferment at 21°C for 10-12 hours until it doubles in size. Adjust time as needed depending on home temperature.
02 -
Lightly flour your work surface and pat the dough into a rectangle. Roll out the dough into a 12"x17" rectangle. Combine frozen raspberries, granulated sugar, and cornstarch in a bowl, mashing the raspberries into small pieces. Spread the filling across the dough, leaving a 1-inch margin lengthwise. Roll the dough tightly starting from the long side opposite the margin. Wet the margin with water to seal, and let the roll rest seam-side down. Slice the dough into 12 equal rolls using a wet non-serrated knife. Place rolls in a 9x13 inch pan, cover with a damp cloth, and let rise until half their original size. This second rise should take about three hours at room temperature.
03 -
Preheat the oven to 350°F and bake the rolls on the center rack for 30-35 minutes. For the frosting, whip cream cheese, butter, lemon juice, and powdered sugar until smooth. After baking, let rolls cool for 15 minutes before spreading frosting over them. Optionally top with lemon zest before serving.