Grate the potatoes with a box grater or be a bit lazy (like me) and use the grater attachment in your food processor. Place the grated potatoes in a strainer lined with cheesecloth. Sprinkle with all but one tiny pinch of the salt.
Next, thinly slice the onion and toss with the potatoes. Gather up the cheesecloth and squeeze out the water. Pull apart.
Whisk together the egg, flour and remaining pinch of salt. Squeeze the cheesecloth wrapped potatoes again.
Fold the strained potatoes into the flour and egg.
Pour enough oil in a skillet to coat the bottom generously. Place over medium heat. Once it is shimmering dollop in the pancake. Sear on one side until the bottom is golden and easy to flip. Turn over and sear on the other side for a few more minutes until the bottom is golden.
Repeat with the remaining batter, adding more oil as needed and scraping out any burnt bits.
Keep the latkes warm in an oven on very low heat, ideally spread out on a baking sheet. Serve them as soon as the batch is done with a dollop of sour cream, creme fraiche or other fun toppings.
Making Ahead or Heating Any Leftovers
Prepare all of the latkes and spread out on a drying rack to cool, some of the excess oil will drip off, too. Package and store up to one day ahead.
To heat, preheat the oven to 375. Spread on a baking sheet and warm for 5 minutes, flip over and continue to bake until the center is hot to the touch.