The night before: Grate the cold butter into a bowl using a cheese grater. Add the flour and use a bench scraper or pastry cutter to blend the butter into the flour until crumbly. Mix in the sourdough discard, buttermilk, honey, and salt using a spatula until the dough forms. Cover and leave the dough at room temperature for 10–12 hours. Do not incorporate the baking soda or baking powder at this stage.
The next morning: Prepare the filling by combining brown sugar and cinnamon in a small bowl. In a separate dish, mix the glaze components and set aside. Preheat your oven to 375°F (190°C) and grease a 12" cast iron skillet with butter.
Combine baking soda and baking powder in a small bowl, then sprinkle over the dough and integrate with your hands. On a floured surface, roll the dough into a 12"x24" rectangle, dusting the top as needed.
Brush the dough with melted butter, then evenly distribute the cinnamon-sugar mixture across the surface, leaving a ½-inch margin along the edges. Roll the dough from the long side into a log and slice into 12 equal pieces using a bench scraper. Arrange them in the skillet, spacing them slightly apart.
Bake for 35–40 minutes until golden. While baking, stir the glaze once more. When the rolls come out hot, pour the glaze over them immediately.