Classic Scandinavian Fish Cakes

3 cups flaked whitefish
1/2 cup mashed potatoes
1-1/2 tbsp. onion, grated or chopped
1 tsp. celery, finely chopped
1 tsp. parsley flakes
1 tsp. chives, chopped or dried
1 egg, lightly beaten tomato sauce

Salt and pepper fish to taste. Mix all ingredients together and add just enough tomato sauce to make the mixture moist. Shape mixture into 2 1/2" rounds or squares, 1/2" thick. Sprinkle with paprika and pan fry slowly in butter or margarine until golden brown on other side. Fry slowly so cakes will set and not break apart when turning. Serve hot.