Prep: Slice 2 pounds russet potatoes into fries, transferring to a bowl of tepid water as you go. Heat 2 inches of peanut or vegetable oil, shortening, lard, or a combination of fats in a deep wide pot over medium heat until a deep-fry thermometer registers 375 degrees F. Drain the potatoes and dry well. Fry: Add half of the potatoes to the pot and fry, stirring gently, until they soften and blister, 3 to 4 minutes (do not let them color). Remove with a slotted spoon or skimmer to a paper towel-lined baking sheet. Repeat with the remaining potatoes. Transfer to the freezer until firm, at least 1 hour. Refry: When ready to serve, reheat the oil to 375 degrees F over medium-high heat. Working in 4 small batches so the oil stays hot, fry the potatoes until golden brown, about 5 minutes. Transfer to fresh paper towels to drain. Season with salt.