In a microwave-safe container, combine milk & butter and microwave at 30-second intervals until butter is completely melted. Let cool to less than 100° before proceeding.

Add the milk and butter to a large mixing bowl or the bowl of a stand mixer. Mix slightly just to stir up the melted butter. Add the eggs, sourdough starter, and granulated sugar and mix on low-medium speed until well combined.

Add the flour in small parts until fully combined, then add the salt.  Mix with a dough hook until dough starts to come away from sides of bowl, or up to 10 minutes. Cover and let rest until doubled in size, or up to 12 hours; or cover tightly and let sit 24 hours in the fridge.

If you have refrigerated your dough, remove from the fridge and allow to come to room temperature. Make sure your desired cinnamon roll filling is ready to spread and roll out the dough to a rectangle roughly 1/4" thick. Spread the filling evenly over the dough and roll tightly, pinching the seam closed.

When ready to assemble preheat the oven to 375°. Prepare a dutch oven, casserole dish, or springform pan by greasing it or lining it with parchment paper, if desired. Using a knife or dental floss cut the cinnamon rolls about 1" thick and place them in the baking dish. Cover and let rise for 30 minutes, or until puffy.

Bake, covered, for 20-25 minutes. Remove cover and bake for an additional 10-15 minutes or until rolls are browned to your liking. Remove pan from the oven and allow to cool for as long as you can stand it. Serve warm with a dollop of icing and a piping hot drink!