Peel and cut potatoes into bite-sized chunks so they all cook evenly
Place the potatoes in a pot with cold water over high heat, once they come to a boil, turn the heat down to a simmer. Check different potatoes by inserting a fork into them. Once the fork slides in and out with ease, take off the heat and strain out all of the water.
Mashed the potatoes well with a potato ricer or masher. Mix in the scallions, season with salt and pepper to taste, then set aside to cool.
Portion and form the potato mixture into even oblong cylinders. Coat each one in the flour, then egg, then coat well with breadcrumbs.
Heat the oil in a saucepan or small skillet and fry the croquettes until all sides are golden brown and crispy. Then place on paper towels to drain any excess grease before serving.