In a large bowl, stir together the mashed potatoes, cheddar cheese, scallions, parsley, garlic powder, Dijon mustard, egg, and 3 tbsp flour until combined.

Using your hands, divide the mixture into 12 portions. Roll each portion into a compact ball, then flatten it into a pancake about 1/2 inch thick. Place the remaining 1/2 cup flour in a shallow dish and dredge each pancake in the flour.

Heat 3 to 4 tbsp of vegetable oil in a large sauté pan over medium heat, adding enough oil to coat the bottom. Fry the pancakes in batches until golden brown and crispy, 3 to 4 minutes per side. Add more oil as needed between batches. Avoid overcrowding and flipping too early. Transfer the pancakes to a paper towel-lined plate and sprinkle with salt.

Serve with sour cream and extra chopped scallions. Enjoy!