Begin by heating the milk until it reaches a temperature of 110 degrees F. You can do this either by gently warming it up in the microwave for about a minute or on the stove. I suggest using an instant-read thermometer to make sure it's the right temperature.
Take the warm milk and pour it into the bowl of a stand mixer along with the sugar, melted butter, and beaten egg. Whisk together until combined.
Next, add 4 cups of flour to the mixer, along with the instant yeast and the kosher salt.
Attach the dough hook to your mixer, and knead the dough on medium speed until it starts to come together.
Once the dough comes together, keep kneading the dough for about 4 to 5 minutes. If the dough isn't quite pulling away from the sides of the bowl as it kneads in the mixer, begin to sprinkle in a couple of tablespoons of flour until it does.
Once your dough is perfectly kneaded, take a large bowl and coat it with cooking spray. Transfer your dough to the bowl, then cover it up with plastic wrap. Let it rise until it doubles in size, which can take anywhere from 30 to 60 minutes, depending on how warm your kitchen is.
Punch down the dough to let out any extra air. Remove from the bowl and use a bench scraper or a knife to divide the dough into 15 equal-sized pieces. You can use a kitchen scale to weigh the pieces of dough for rolls that are exactly the same size.
Roll each piece of dough into a ball and place the balls into a 9x13 baking pan that is coated in cooking spray.
Cover your rolls plastic wrap and let them rise again until they've doubled in size.
While your dough is rising, preheat the oven to 375 degrees F.
When the rolls have doubled in size, place the pan into the preheated oven and let the rolls bake for 17 to 20 minutes, or until they are golden brown.
Remove the rolls from the oven. The next step is completely optional, but highly recommended. Brush your rolls with melted butter and sprinkle a touch coarse salt on top. Cut the rolls apart, then serve and enjoy.