In a stand mixer, combine your active sourdough starter, dark brown sugar, and warm whole milk (around 100°F). Mix on low speed until smooth and slightly bubbly.

Gradually mix in the softened unsalted butter, salt, and a large egg. Slowly incorporate the bread flour until the dough pulls away from the sides and forms a smooth ball.

Transfer the dough onto a floured surface and knead for about 5 minutes until smooth and elastic.

Place the kneaded dough in a greased bowl, cover with a damp cloth, and let it rise until it has increased in size by at least 50%, about 3 to 7 hours.

Roll the dough out into a rectangle about 1/4-inch thick. Spread softened butter, then sprinkle ground cinnamon and dark brown sugar mixture on top.

Roll the dough tightly from one edge to the other and slice into 9 equal pieces.

Cover the baking dish with a kitchen towel and let rolls rise until puffy, about 2 to 4 hours.

Preheat your oven to 350°F.

Pour heavy cream over the rolls before baking. Bake for 30 to 35 minutes until golden brown.

Let the rolls cool for about 10 minutes, then frost with cream cheese frosting.