Mix together the starter, flour, yeast, salt, sugar, powdered milk, oil, melted butter, potato, orange juice, and liquid milk in the stand mixer. Mix/knead it at medium speed for 5 minutes. Transfer dough to an oiled bowl to rise in a warm space for about 90 minutes. (I preheated my oven for 1 minute before turning off the heat, and put the dough in the warmed oven to rise for 90 minutes). (I accidentally let it rise an additional 30 minutes as I was baking something else at the time.)
Pat out dough into a 16x9 inch rectangle and spray the surface with oil. Mix together the sugar, flour, and cinnamon, and spread that over the surface of the dough. Roll up the dough so you have a 9-inch log. Pinch together the seams and tuck them in at the ends, and place the loaf seam-side down in a greased 9x5 inch loaf pan. Let the loaf rise in a warm space until the dough is about an inch over the top of the loaf pan. (This took about 45 minutes since my oven was running, but the recipe said it could take 90 minutes.)
Heat oven to 350F. Bake the loaf for 10 minutes, then cover the top with foil to prevent additional browning and bake it for an additional 35 minutes (the recipe said 40-45 minutes), until the temperature of the loaf is 190F.
Adapted from King Arthur Flour