Warm the milk and butter in a microwave-safe bowl for about 30-40 seconds, until the butter is mostly melted and the mixture is warm (but not hot). Stir well.
Pour the warm milk mixture into the dry ingredients. Add the egg and mix on low speed until smooth. Increase to high speed for 2 minutes. The mixture will be wet and sticky—this is normal.
1 large Egg
Switch to the dough hook attachment. Add 190 g more flour and knead on low speed until mostly incorporated. Scrape down the sides of the bowl as needed. Add the remaining 120 g of flour.
Continue kneading on medium-low speed for about 10 minutes. Stop occasionally to adjust the dough on the hook. The dough should be smooth and elastic. To test, stretch a small piece between your fingers—if it stretches thin without tearing, it’s ready.
Transfer the dough to a lightly oiled bowl. Cover with a damp towel or plastic wrap and let it rise in a warm place until doubled in size, about 1 hour.
Meanwhile, mix the filling. In a small bowl, combine brown sugar, cinnamon, and a pinch of salt.
135 Grams Light brown sugar, 1 Tablespoon Ground cinnamon, Pinch Salt
Once the dough has risen, turn it out onto a floured surface. Roll it into a 30 cm x 45 cm rectangle (wide side facing you).
Spread the softened butter evenly over the dough.
60 Grams Unsalted butter
Then sprinkle the cinnamon sugar mix over the top. Use your fingers to gently press the sugar into the butter.
Starting from the long edge closest to you, roll the dough tightly into a log. Pinch the seam to seal.
Use a sharp knife to cut the log into 12 even rolls.
Place the rolls into a parchment-lined 23 cm x 33 cm (9 x 13 inch) baking dish. Cover and let rise until doubled in size, about 1 hour.
Preheat the oven to 175°C (350°F). Once risen, bake the rolls for about 30 minutes, or until golden brown.
While the rolls cool for about 15 minutes in the pan, make the glaze icing. Whisk the icing sugar, water and vanilla, until combined and runny. Add another tbsp of water if needed for a more pourable consistency.