Add green onions and egg to mashed potatoes and mix together.
Season with salt and pepper
Form mixture into hamburger shaped patties.
Heat oil and butter in non stick pan over medium low heat.
Fry patties allowing the underside to brown until crisp before flipping them over to fry the other side. Add more oil or butter if needed once you flip them.
Keep finished potato pancakes on a plate in the preheated oven to keep hot.
Serve potato pancakes with sour cream or chili sauce.