Do not overheat your milk! The ideal temperature for activating yeast is 100-110 degrees F. (My sweet spot is usually 105 degrees F) Anything hotter will instantly kill the yeast and the yeast will not rise. Measure the temperature with a thermometer to make sure it is at the right temperature.
Make sure to use room temperature butter. Using softened room temperature butter will allow even mixing into the dough without making the dough overly wet. Moreover, if you use melted butter for the filling it will cause the filling to leak out before baking.
Use a room temperature egg. Using a cold egg may shock the dough and may affect the yeast preventing the dough from rising.
If the dough is too wet, add 1-2 more tablespoons of flour. The dough should be fairly tacky and may stick to your hands but should come off cleanly. However, if you feel like the dough is too wet to be manageable knead in 1-2 more tablespoons of flour.
Flour your work surface and rolling pin before rolling out the dough. The dough may be fairly sticky since it is a wetter dough. To prevent any tearing, make sure the work surface and rolling pin are generously floured.
Rub the brown sugar into the butter. When you spread the cinnamon sugar across the buttered dough, remember to gently rub the sugar into the dough so that it is well combined and sticks to the dough.
Storage Instructions
These rolls are best served immediately. For any leftovers, cover in an airtight container or with plastic wrap tightly and store at room temperature for up to 3 days.