Place sweet potato in a pot, covered with water, and bring to a boil. Reduce heat and simmer, covered, for about 40 minutes or until fork tender. Remove from water to a bowl and allow to cool. When cool enough to handle, remove skin with a paper towel and discard. Mash the sweet potato with a fork, mix in milk.
Spray a 12 cup muffin pan with cooking spray.
Bring the chicken broth to a boil in a medium saucepan. Whisk the polenta and 1/2 teaspoon of salt into the broth and cook over low heat, stirring often, until the polenta thickens, about 15 minutes. Stir in the Parmesan cheese. Remove from the heat, then fold in the sweet potato and mix well to combine.
Spoon the polenta evenly into the prepared muffin pan. Cover with plastic wrap and refrigerate for a few hours or overnight, until firm. If needed right away, place in freezer till cold, about 30 to 45 minutes.
Heat about 1 or 2 tablespoons olive oil in a large skillet. Remove polenta from muffin pan and cook over moderate heat until browned on the bottom, about 3 minutes. Carefully turn the polenta with a metal spatula, and cook another 3 to 5 minutes till browned and slightly crispy.
Chile Colorado adapted from Everydaypaleo.com