Cook sweet potato until tender. (See baking tips.)
Heat up milk to 105°F – 110°F; add yeast and sugar and stir. Let bloom for 5 – 10 min.
Once yeast is bubbly, add 3/4 cup sweet potato, 1 egg, and melted butter and blend with an immersion blender until smooth.
Add wet mixture into a stand mixer fitted with a dough hook. Add the salt and most of the flour and begin mixing on medium-low speed.
Knead the dough for 10 – 20 min., sprinkling in remaining flour if needed until the dough has formed a ball and has stopped sticking to the sides of the bowl. Shape the dough further into a ball and place in a greased bowl. Lightly grease the top of the dough, then cover and set in a warm area to rise until doubled in size, about 1 hour.
Sift together the powdered sugar and the cinnamon into a bowl and set aside. Whisk 1 egg and set aside. Grease your loaf pan and set aside.
Punch the dough down once risen and place on a lightly floured surface. Roll to an 8” x 20” rectangle, dusting with flour as needed.
Brush the egg generously over the rectangle until it is covered (save some of the egg wash for later).
Using a sieve, sprinkle all of the cinnamon sugar mix over the dough evenly, leaving about 1/2” border on one short side.
Starting with the other short side, tightly roll dough into a log. Set the log into the prepared loaf pan and cover. Let rise 1 hour or until doubled in size.
Preheat oven to 350°F. Once the dough is risen, brush the top with the remaining egg wash.
Bake for 30 – 35 min. or until center reaches 200°F. Let loaf cool completely before slicing. Serve with unsalted butter if you like.
