Cut the cold unsalted butter into the flour until crumbly. Stir in the buttermilk, sourdough starter, and honey until the dough comes together. Cover the dough and let it rest for 8 hours or overnight—this is where the magic of sourdough happens!

Preheat your oven to 375°F (190°C). Prepare two round baking pans by greasing them with butter or oil.

Sprinkle the dough with baking powder, salt, and baking soda, then knead it gently until everything is well incorporated.

Generously flour your countertop and the dough to prevent sticking. Roll the dough out into a 20x12-inch rectangle.

For the filling, mix the brown sugar and cinnamon together. Brush the dough with melted butter, then sprinkle the cinnamon-sugar mixture evenly across the surface, leaving a small border around the edges.

Roll up the dough tightly from the shorter side to form a log. Use a bench scraper or sharp knife to slice the log into 12 equal rolls.

Arrange the rolls in the prepared pans with a little space between them to allow room for rising. Bake for 35-40 minutes, or until the rolls are golden and your kitchen smells heavenly.

While the rolls bake, whisk together the confectioners' sugar, melted butter, milk, and vanilla extract for the icing.

As soon as the rolls come out of the oven, drizzle the icing over the top so it melts into all the gooey crevices. Serve warm and enjoy!