We've been making these as an incredibly crunchy side-dish for a few years now. We can't find anybody that can eat just one mouthful. Super-slender tendrils of potato, golden brown, with a crunch that disintegrates in your mouth. Can't stop eating them.
The trick, other than the fine "shreds" is "Doble Frita" -- Double Fried.
This is surprisingly simple.
You'll need about 1 medium potato per serving.
Plenty of deep-fry oil.
Seasoning to make you happy. Try lemon pepper or Tajin, to taste. Salt as needed.
Tons of toweling for drying the spuds and draining them of oil.
Run the potatoes over the julienne attachment of your mandolin slicer (this critter). It's the one with all of the tiny close-set blades on the feed bed of the mandolin.
For real fun, slide the potato back and forth across the blades which cuts some of the julienne "sticks" to "fuzz" thickness. The sticks (shreds) are about the size of a wood pencil lead. The fuzz is about the thickness of a 0.5mm mechanical pencil lead.
Depending on your potato type, as in Costa Rica, you should wash the potato shreds under running water until the milky starch stops running out.
Drain them well.
Better than that. Get them really dry.
Get your oil up to a solid 350F (177C).
CAREFULLY drop a small handful of the shreds into the hot oil. Watch the boil-up. If it is safely well below the top rim of your pot, you can add up to about a half potato's shreds. When the boil-up subsides watch the "fuzz" pieces and pull the batch out just as they show slight browning. If you don't have any fuzz, pull the batch when they're lightly golden.
Drain the batch on paper towels.
Bring your heat back up to temperature and repeat until all potato is cooked through this first cycle.
Take the heat of the oil up to 370F (188C).
ATTENTION: This next step happens fast. Do not drop the fries into the hot oil and turn away or get distracted.
Grab up about a full potato's worth of shreds and gently slide them into the hotter oil. Keep them submerged. In about 10 to 20 seconds, the fries will go to a dark golden brown.
Pull them out quickly to drain. Repeat to finish the batch.
Season to taste.
Please eat responsibly. We're not responsible for your overeating episodes.