In a glass measuring cup, microwave the milk for 90 seconds, but do not allow to boil.
2/3 Cup Milk
Remove from microwave and add the butter to the milk.
5 Tablespoons Unsalted Butter
Stir to combine and allow the butter to completely melt.
Once it is warm but not hot, add the sugar and yeast and set aside.
3 Tablespoons Granulated Sugar, 1 teaspoon Dry Active Yeast
In the bowl of a standing mixer, add the flour, salt, vital wheat gluten on the opposite side of the bowl as the salt, and mix with a paddle attachment or stir by hand.
1 Cup Sweet Potato, 1 Large Egg with 1/2 Tablespoon Egg White Removed
Mix again just until the dough comes together and then switch to the dough hook and mix for 90 seconds.
Drape a light towel or saran wrap over the bowl and allow to rise for 1-2 hours.
Sprinkle the counter lightly with flour and turn the very soft dough out.
Sprinkle the top with a little more flour and roll out to about 1/4-inch thick rectangle.
Starting at the end closest to you, pinch the dough closed and tightly roll into a log.
Cut about 2-inch pieces and using the palm of your hand, gently roll the dough into balls. (Watch the video in the post for additional help.)
Place on a greased cookie sheet and cover with another towel or saran wrap.
Allow to rise for 1-2 hours.
Heat the oven to 350 degrees F and bake for 18-20 minutes, then quickly brush the tops with more butter and serve.
Butter
Notes
You have a few options for make ahead:
You can make the dough, wrap in plastic wrap in the bowl, and let sit in the fridge overnight, then allow to come back to room temperature for an hour or two and proceed as normal.
You can also make the dough, roll out into rolls on the pan and cover with plastic wrap in the fridge, then let rest at room temp for an hour or two in a warm place and bake as normal.
Or you can bake them completely the day before, leave them on the pan and cover with foil once cool and then reheat with the foil over them in a 350F oven until warm.