Bloom the yeast: In a large mixing bowl, whisk together the warm water, sourdough discard, and yeast. Let the mixture sit for 10 minutes until foamy.
Mix the dough: Add the flour, eggs, melted butter, honey or maple syrup, vanilla, baking soda, baking powder, and salt to the bowl.
Knead the dough:If using a stand mixer: Attach the dough hook and knead on medium speed for 6–8 minutes, or until the dough is smooth, elastic, and pulls away from the sides of the bowl.If kneading by hand, turn the dough out onto a lightly floured surface and knead for 8–10 minutes until soft, smooth, and stretchy. First rise: Transfer the dough to a greased bowl, cover it, and place it in a warm spot. Let it rise for 60–90 minutes, or until doubled in size.
Make the filling: In a small bowl, combine the softened butter, brown sugar, and cinnamon until a smooth paste forms. Set aside.
Preheat the oven to 375°F.
Shape the rolls: Turn the risen dough onto a lightly floured counter. Roll it into a ¼-inch thick rectangle. Spread the cinnamon-sugar filling evenly over the surface. If your butter isn’t soft enough to spread, crumble it evenly across the surface of the dough. It will melt and distribute evenly as it bakes. Starting from the long side, roll the dough up tightly and pinch the seam to seal. Slice into 12 equal rolls.
Prepare the pan: Place the rolls in a greased cast-iron skillet or 9×13 glass baking dish, evenly spaced.
Bake: Bake for 20–25 minutes, or until puffed and lightly golden.
Make the glaze: In a small saucepan over medium heat, whisk together the cream cheese, milk, maple syrup, vanilla, and a pinch of salt until smooth. If the glaze is too thick, add milk 1 tablespoon at a time until it reaches a pourable consistency.
Glaze: Spread the glaze over the warm rolls and serve.