potatoes - watch the video to see (peeled and cut into uniform fries)
water - enough to cover potatoes (for par boiling with salt and vinegar)
salt - watch the video to see (added to par boiling water)
vinegar - watch the video to see (added to par boiling water to help keep shape)
duck fat - enough for deep frying (a large amount) (for deep frying)
Instructions
Prepare Potatoes: Peel the potatoes and cut them into uniform fries.
Par Boil Potatoes: Par boil the cut potatoes in salted and vinegar-spiked water for 15 to 20 minutes or until they are very nearly falling apart.
Cool Potatoes: Drain and allow the potatoes to cool completely on a wire rack set in a rimmed baking sheet.
First Fry: Heat duck fat to 275°F (135°C). Fry the potatoes slowly at this temperature until they turn just golden blonde without any browning.
Second Fry: Increase the duck fat temperature to about 360°F (182°C), just below its smoke point. Fry the potatoes again until golden brown, about 5 minutes.
Drain and Serve: Drain the fries on paper towels. Repeat the process with all potato varieties to compare results.