In a large bowl, combine mashed potatoes, cheese, green onions, eggs and 3 tablespoons of flour until smooth. (See Notes.) Using your hands, divide the mixture into 12 units. Fill each serving in a compact ball and then place on pancakes about 1/2 inch thick.
Then put the remaining half of the flour in a shallow pan and pour each pancake well into the flour. Heat 3-4 tablespoons of vegetable oil in a large frying pan over medium heat. (Add enough oil to cover the bottom of the pan.)
Now fry the pancakes piece by piece until golden brown and crispy on both sides and fry for 3-4 minutes. Add more oil to the pan if necessary between batches. (Do not fill the jar or make pancakes too soon. Otherwise, it will not crack.)
Put pancakes on a paper towel and sprinkle with salt. Serve potato pancakes with sour cream and season with additional chopped green onions.
NOTE. The remaining mashed potatoes will vary depending on how much butter, milk or butter is added to the original batch. If the mixture of mashed potatoes and mashed potatoes looks too dry and does not stick, add one more egg. If it looks too wet, add 1 teaspoon of flour at a time until the mixture mixes.