Make the dough: In the bowl of a stand mixer or large bowl, mix water, buttermilk, melted butter, sugar, and yeast. Allow to sit for 15 minutes.
Add eggs and salt, then mix in flour one cup at a time. Once all flour has been added, mix for an additional 5 minutes. Dough should be smooth and elastic.
Grease a large baking dish or jelly roll pan (or a 9-x-13-inch baking dish if you are fine with your rolls touching).
Meanwhile, prepare your filling. Mix granulated sugar, brown sugar and cinnamon together in a medium bowl. Set aside.
On a lightly floured surface, roll dough into a 10-x-12-inch rectangle. Spread melted butter over the surface of the dough, followed by the filling, leaving a ½-inch border all around.
Roll dough lengthwise like you’re making cinnamon rolls, and place onto a parchment paper-lined baking sheet.
Using a pastry knife, make a slice down the center of the roll leaving ½ inch at the top of long roll. With the cut side up, twist the dough ropes and tuck the ends under. Cover with a tea towel and let rise for 15-20 minutes.
While twist is rising, preheat oven to 375 degrees F.
Bake for 18-24 minutes or until lightly golden brown.
While rolls are baking, mix all frosting ingredients together in a large bowl, starting with 3 tablespoons milk and adding more as needed to reach a spreadable consistency.
When twist come out of the oven, immediately spread a layer of frosting on warm rolls. Add another layer of frosting once cooled, if desired.