Into the bowl of your stand mixer (or in a large mixing bowl), add the warm milk, the sugar and the yeast. Mix together with a fork.
Add the melted (and cooled) butter to the milk mixture. Be sure the melted butter isn't too hot or it will kill the yeast.
Add the egg to the milk mixture.
Add the flour and salt to the bowl on top of the milk mixture and set the mixer to low speed (use the dough hook for this). If making by hand, mix with a wooden spoon.
After about a minute you should see a sticky dough starting to come together. Scrape down the sides of the bowl if necessary.
Turn up the mixer speed slightly and allow the mixture to knead the dough for about 2-3 minutes. The dough should be tacky to the touch, but not so sticky that it's very messy. It should pull away from the sides of the bowl easily and the bowl should appear fairly clean.
If you don't have a stand mixer, you can knead the dough by hand on a lightly floured work surface for 3 minutes after the wet and dry ingredients are combined.
Cover the bowl with some plastic wrap and place it inside another large mixing bowl. Pour some hot water (from the tap or recently boiled kettle) between the two bowls to gently heat up the dough. This will help it rise very quickly. Be careful not to use water that's too hot as this will cook the dough that's touching the mixing bowl. Also, be careful not to get any water into the bowl with the dough (See the information in the blog post for more tips on how to do this!). Let the dough raise for 20 minutes.
While the dough raises, grease a large cast iron skillet (or a 9-inch by 13-inch baking dish also works) with butter.
In a separate bowl, combine the brown sugar and the cinnamon. I use 1 tbsp of cinnamon, but feel free to use a little less if you'd prefer a more subtle taste.
Turn the dough out onto a work surface that's been very lightly greased with vegetable oil. Using a rolling pin, roll out the dough evenly until you have a rectangle that's approximately 18 inches wide and 12 inches deep. Brush the dough with the melted butter. Spread the brown sugar and cinnamon mixture evenly over the dough.
Roll up the dough from the long side until you've got one long roll. Cut the long roll in half, then in half again, and then each of those sections into 3 pieces until you have 12 cinnamon rolls. Try to cut the rolls to an even thickness as this promotes even baking. You don't want some rolls to be overdone and others to be raw in the middle.
Arrange the 12 pieces in the pan you've greased.
Place the cinnamon rolls in a cold oven and set the oven to bake at 375 degrees Fahrenheit. The cinnamon rolls will rise for a second time in the oven as it preheats.
Set the oven timer for 23 minutes. When the oven timer goes off the cinnamon rolls should be baked to a golden brown colour. If 2-3 more minutes of baking are required, allow the rolls to bake for a few additional minutes (every oven preheats differently, so watch them around the 20-minute mark if your oven preheats very quickly!).