1.Place the mashed potatoes in a large bowl. Gently mix in the onion, flour, beaten eggs, salt and pepper.
2.Form mixture into 6-8 balls, flatten them into pancakes and place them on a plate. Cover and refrigerate the until ready to use.
3.In a large skillet, heat cooking oil over medium-high heat. Add 3 pancakes at a time to the hot oil, being careful not to crowd pan. Fry for about 3-5 minutes per side, until cakes are brown and crispy.
4.Remove the finished pancakes to a plate or baking sheet lined with paper towels and keep warm in a 200°F degree oven. Repeat process with remaining potato mixture until all the pancakes are made.
5.Sprinkle the pancakes with the chives and serve with sour cream, etc.