Place 2 tablespoons of olive oil in a large skillet and saute the onions over medium to low heat until transparent and soft, about 10 to 15 minutes. Set aside to cool.

In a large bowl, mix the onions, grated potatoes, eggs, flour or potato starch, salt, and pepper until combined well. 

Place the mixture into a large colander and set it over a large bowl to drain any excess liquid for about 10 to 15 minutes. Pour the latke mixture into a large bowl and set aside. Discard the liquid that was drained out of the latke mixture and scrape off the layer of potato starch that forms in the bottom of the bowl. Place the starch back into the latke mixture and combine well. This will help bind the latkes as they cook.

Heat the rest of the olive oil and canola oil in a large skillet over medium heat. The oil should be about ½  inch deep. After 2 to 3 minutes, test the heat of the oil with a tiny amount of latke mix. If the mixture sizzles the oil is at the right temperature to begin frying.

Scoop a heaping tablespoon of the latke mixture into your palms and flatten it into a 3 to 4 inch patty. Gently place the latke into the oil and fry until golden brown, about 2 to 3 minutes per side. Continue frying in batches of about 4 to 6 latkes at a time, making sure not to overcrowd the pan. Place the finished latkes onto a towel-lined tray to absorb any excess oil.

Serve the latkes warm with applesauce and/or sour cream.