Boil potatoes in water, they should be on the firm side. Drain, mash with butter. Set aside while you make the chicken filling. Combine all filling ingredients, except oil and tomato sauce. Saute mixture in the oil, then add the tomato sauce. Cool.
Form potato mixture into 4-inch diameter balls. Poke a hole in the middle of each ball, fill with chicken mixture; reform balls.
Coat each ball with egg, then coat with flour. Fry in canola oil until golden brown.