Heat a thin layer of oil in a cast iron skillet over medium heat.
While the oil comes up to temperature, shred the sweet potato using the large holes on a box grater, and chop the scallions. Mix the veggies together with the beaten egg, flour, ½ teaspoon garlic powder, and ½ teaspoon salt.
Place ⅓ cup dollops of batter into the hot oil and press to flatten using a fork or spatula. Cook on one side until golden brown, 3 to 5 minutes. Flip and brown the other side for 2-4 minutes. Transfer to a paper towel lined plate and repeat with the remaining batter.
To make the Chipotle Mayo, mix the mayo, chipotle powder, garlic powder, and salt in a small bowl.
Serve hot with a dollop of chipotle mayo and more sliced scallions to garnish.