In a large bowl whisk together 2 and ¼ cup flour, yeast, sugar and salt.
Warm the buttermilk to the temperature described on your yeast package (likely about 115F degrees to 125F degrees - it should be warm but not scalding) - then stir the buttermilk, melted butter and egg into the flour mixture using a large rubber spatula or wooden spoon.
Once the batter starts to form and pull away from the edges of the bowl, turn it out of the bowl onto a floured surface/kitchen top. If the mixture still appears very wet stir in the additional ¼ cup flour, 1 tablespoon at a tim
Knead the dough with floured hands for about 4 minutes until the dough becomes smooth and forms a ball. You may need to flour your hands a few times in between. Then place the dough into a lightly greased bowl to rest for 10 minutes.
While the dough is resting, stir together granulated sugar, brown sugar and cinnamon to make the filling.
Then on a flat lightly floured surface or a silicone baking mat roll the dough into a rectangle shape about 14 by 9 inches in size. Spread the ¼ cup of very soft butter over the rectangle and sprinkle the cinnamon sugar mixture over top, leaving an border of about ½ inch on each side.
Then starting at the short edge of the rectangle, roll the dough into a roll and pinch the side closed. Using unflavored dental floss or a very sharp knife cut the roll into about 8-10 slices, each about 1 inch thick.
Line a 9-inch springform pan with parchment paper, or lightly grease a 9 inch pie plate and place the rolls inside. Allow to rise for 60 to 90 minutes in a warm, draft free environment - such as inside an oven (that's turned off).
If your rolls are in the oven to rise, remove them. Then preheat the oven to 350F degrees and bake the rolls for 20-25 minutes in the preheated oven until the tops are just starting to brown.
Remove the cinnamon rolls from the oven.
As they're cooling make the glaze. In a medium sized bowl whisk together all the glaze ingredients. Once smooth and no sugar lumps remain, drizzle on top of the cinnamon rolls.