Start by peeling your potatoes one at a time and shredding them with the large holes of a box grater into a bowl of ice water. You should have about 5 cups of potatoes. Grate the onions into there too. Let sit for 10 minutes.
Remove potatoes, squeezing out the moisture into the water. Dry potatoes very well with towels or cheesecloth and keep covered. Let the water sit for 5-10 minutes for starch to accumulate on the bottom. Carefully drain water, reserving the white starch on the bottom. This part is optional, but helps make crispier latkes with soft insides. You can also add potato starch to the potato mixer directly, but why do that when you already have it in the potatoes?!
Place potato/onion mixture in a large bowl, dry again very well. Then add in the eggs, flour and salt and reserved dried off starch and combine.
Set up a cooling rack over paper towels.
Meanwhile, heat up about 1/4 inch of canola oil in a large (cast iron) saute pan. A dab of schmaltz never hurt either. Pro tip- add a little piece of peeled carrot to the oil to soak up the brown bits that flake off so they don't get in your latkes!
Scoop heaping 1/4 cup spoonfuls of the potato mixture into the oil (they should sizzle!) and flatten slightly and fry until golden brown, about 3 minutes. Don't worry about your latkes being perfectly round. Those fly away pieces get extra crispy and delicious! Then flip and fry the other side another 2 minutes or so. Don't overcrowd the pan.
Repeat with remaining latke batter, drying it again if liquid starts to accumulate. Drain on a rack over paper towels and sprinkle with more salt. Eat!