In the bowl of a stand mixer, combine the sourdough starter, eggs, milk, melted butter, and sugar or honey.
Add the flour and salt, then knead with the dough hook for about 10 minutes until the dough is smooth and pulls away from the sides of the bowl.
Cover the dough and let it rest for 20 minutes. Perform 2 to 3 sets of stretch and folds, resting the dough for 20 minutes between each set.
Once the dough passes the windowpane test, transfer it to a lightly oiled bowl, cover tightly, and let it ferment overnight in a warm place for 8 to 12 hours, or until doubled in size.
The next day, mix together the filling ingredients: softened butter, brown sugar, cocoa powder, and espresso powder. Roll the dough into a large rectangle about ¼-inch thick, spread the filling evenly over the surface, then use a pizza cutter to make 6-8 strips then, roll each slice.
To make the gooey bottom just melt the butter then mix in the brown sugar and espresso powder in a small bowl. Spread it over the bottom of the baking pan you will be using. Arrange the rolls in the baking dish, cover, and let rise for 1 to 2 hours.
Before baking, pour the heavy cream evenly over the rolls. Bake at 375°F for 25-30 minutes, or until golden brown.
While the rolls cool slightly, beat the cream cheese until smooth. Add the mascarpone, then the milk or heavy cream and powdered sugar, mixing until light and creamy.
Spread the frosting over the warm rolls and finish with a generous dusting of cocoa powder before serving.
