In a large bowl, whisk the flour, yeast, sugar and salt.
Melt your milk, butter and water on low heat until smooth. Make sure the tempearture of the mixture is in and around 110°F. when you add it to the flour mixture. Add the egg to the bowl too and use your hands to combine to form a soft dough.
Lightly flour a clean work surface and knead your dough for 3 minutes. Transfer to a lightly sprayed bowl, cover loosely with a towel and let it rest for 10 minutes.
Next, roll out the dough into a 14 x 8" rectangle. Spread the softened butter out evenly. Mix the cinnamon sugar together and then sprinkle it all over.
Time to roll up the dough the long way (see video) - not too tight but not too loose. Cut into 12 even rolls and transfer to a greased baking dish. They should not be touching. Cover the dish tightly with aluminum foil or plastic wrap and place in a draft-free, warm environment to rise for 60-90 minutes. They should double is size.
Preheat your oven to 375° F. Bake the rolls uncovered for 25-28 minutes. Keep an eye on them and if they start to brown too much, loosely cover/tent them with aluminum foil.
Allow them to cool for 1 hour and then whisk together the icing ingredients until smooth and drizzle on top of the rolls.
Notes
Recipe slightly adapted from Sally's Baking AddictionI used a 10.5 x 7.5 inch baking dish but a 9 inch round should work too.Store at room temperature in an airtight container for up to 3 days. Store in your fridge for up to 5 days. Make Ahead: The dough ball can be made the night before. Cover it with plastic wrap and let it rest in the fridge over night. The next morning, remove from your fridge and let it rest in a warm environment for 1 hour.