Potato vareniki

Ingredients :
2 pounds potatoes, cooked (save water from cooked potatoes) ,
2 onions chopped ,
1 stick margarine ,
Salt and pepper ,
2 cups flour,
1/2 teaspoon salt

Method:
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.
When all are cooked, drain and serve with the remaining sauteed onions on top.