Scrub the potato and, if desired, peel.
Using a box grater or grater attachment on a food processor, shred the potato using the largest holes. Grate potato on the long side to get longer shreds.
Submerge potatoes in a bowl of water and swirl around with your hand. Use a fine mesh colander to strain out the water. Repeat this process 1-2 more times until the water remains clear.*
After potatoes are strained the last time, place them on a linen hand towel or cheesecloth. Squeeze as much water out as possible.
Heat oil in a cast iron or non-stick skillet over medium heat. Add potatoes and onions. Sprinkle salt, black pepper, paprika and cayenne pepper over the mixture and stir to combine.
Allow potatoes to cook undisturbed for about 5 minutes or until the bottom is brown.
Turn in 2 or 3 sections and allow to cook undisturbed 2-3 minutes until the bottom is browned.
Continue turning the potatoes every few minutes until desired crispiness is achieved, about 10 minutes. Add more olive as necessary for potatoes to continue to sizzle. A non-stick pan will require less oil than a cast iron or stainless steel skillet.
Serve immediately.
* At this point, potatoes can be left in water and refrigerated for up to 24 hours.
Hack: Leftover hash browns can be stored in the refrigerator for up to 5 days. To reheat, place in a skillet over medium heat just until warm.