Using a large pot, boil potatoes with skins on until almost done. Allow to cool, and cut potatoes into long strips, approximately 1/4 to 1/2-inch wide and thick. In a large pot or fryer, heat oil to 350 degrees. Par-fry the potatoes for 5 to 6 minutes. Potatoes should be limp. Remove potatoes and place onto paper towels and allow to drain. Let sit for 1 to 2 hours at room temperature.
Cut onions into 1/2-inch wedges. Just before serving time, place potatoes and onions into oil heated to 375 degrees F for 3 to 5 minutes, or until brown. Remove fries from oil, drain on paper towel, and while still hot, season with salt and pepper