To make potato pancakes, combine grated potatoes and onions with egg, scallions and seasoning. Shape the potato-onion mixture into thin, flat pancakes with your palms. Cook in a large skillet coated with oil and flatten further with a spatula. Cook until both sides are golden brown and drain before serving.
To prepare the potatoes, peel 2 pounds of russet potatoes and place in a bowl of cold water. Grate the potatoes in a food processor or a hand grater, along with one medium onion. Place the grated potatoes and onions in fine mesh strainer and squeeze out the excess water into a bowl. Strain the water from the bowl, leaving the potato starch. Mix the potatoes and onions with the potato starch, then mix in one beaten egg, a 1/2 cup chopped scallions, and salt and pepper to taste.
Coat a large skillet with a thin layer of vegetable oil and place over medium heat. Place 2 tablespoons at a time of the potato mixture in the palm of your hand and flatten as much as possible. Place the flattened pancake into the hot oil and cook until golden brown on one side. Flip over and continue cooking until the other side is also golden brown. Remove from the heat and place on paper towels to drain. Serve hot with sour cream and applesauce.