Cook potatoes in simmering water until soft and put them through a Potato ricer. Saute Onion in margarine until very soft, add 1/2 of the onions to the potatoes and season with salt and pepper. Sift flour and salt into a bowl. Add vegetable oil and enough water to make a soft dough and mix until the dough no longer sticks to the hands. Cover dough and let rest for about 15 minutes. Roll out dough on a floured board to a 1/4-inch thickness. Cut dough into small squares and place a dollop of Potato mixture in the center of each square. Fold dough, pinch ends to form a triangle. When all are made, put into boiling water and boil for about 10 minutes.