Heat 1 tbsp canola oil over high heat in a large frying pan. Fry onions until they start to take on colour. Add corned beef and stir until heated through. Set aside. Mix egg yolks and 1/4 cup flour into the mashed potatoes, then add corned beef mixture. Mix well and add salt & pepper to taste. Using an ice cream scoop (or your hands), divide mixture and shape into little cakes about 1 1/2-2" around and 3/4" thick. Dredge cakes in the extra flour and shake off the excess. Heat the extra canola oil over medium-high heat. Once the oil is hot, fry cakes until they are heated through and medium brown on both sides. You should only turn the cakes once. Excessive flipping will cause them to break apart. Makes 6-8 servings.