To keep the patties warm between batches, preheat the oven to 200 degrees F. In a large bowl, combine sweet potato, 1 tablespoon oil, salt, pepper, garlic powder, and chipotle chili powder.
Heat a large cast iron or similar heavy-bottomed skillet over medium-high heat. Add 1/2 tablespoon oil and 1 tablespoon butter. Once the oil is hot and the butter melted, scoop a slightly heaping 1/2 cupful of the sweet potato mixture and drop it onto the skillet in a tight mound.
With the back of a spatula, flatten the sweet potato mound into a hash brown patty (it doesn't need to be a perfect circle). Repeat twice more, so that you have 3 hash brown patties in the skillet.
Cook the patties on both sides, flipping them halfway through until they are nicely browned on both sides and hot and tender in the center, about 6 to 8 minutes total. Transfer the cooked hash browns to a baking sheet and place in the oven to keep warm. Repeat with the remaining oil, butter, and sweet potato mixture.
