In a large mixing bowl, combine your leftover mashed potatoes with the grated cheddar cheese, chopped scallions, parsley, egg, onion powder, and cayenne pepper. Stir gently until well blended. Gradually fold in all-purpose flour until just combined.

Using a ¼-cup measuring cup, scoop up the potato mixture and form thick patties in your hands. Coat each patty in panko breadcrumbs for a delightful crunch.

Heat about 2 tablespoons of avocado oil in a cast-iron skillet over medium heat. Once the oil shimmers, carefully place the potato pancakes in a single layer. Cook for 2-3 minutes on each side, or until golden brown.

Transfer the pancakes to a plate lined with paper towels to absorb excess oil. Garnish with additional chopped scallions and serve hot.