Preheat the oven to 250℉. Peel, wash, then thinly slice potatoes with a mandolin.Add sliced potatoes to a bowl of beef fat and salt, then toss well to ensure each slice is fully saturated.Line a loaf pan with parchment paper, and layer potato slices evenly, one by one.Cover the top with parchment paper, and place in oven for 3 hours or until fork-tender.After 3 hours, remove potatoes from oven, then compress with cans or any heavy object.Place in the refrigerator, and chill for 12 hours.After 12 hours, remove potatoes from the loaf pan, and cut into rectangular segments.Heat vegetable oil to 375˚F, and lower potatoes into pot, deep frying for 3-5 minutes until golden brown.Remove from the pot, then let cool before sprinkling with salt. Enjoy!