Heat the oil on medium high heat. I do not own a thermometer, so I just check by taking a small piece of potato and placing it in the oil.
Drain the potatoes throughly by wringing them out in a tea towel, removing as much water as possible. Place in a large mixing bowl. Repeat the same process with the onions and place in the same bowl.
Add the eggs, egg yolk, cornstarch and chives. If the mixture seems too dry, add another egg yolk. Stop the process here if you want to make this ahead of time.
Right before frying, add the salt and pepper, and mix. Using an ice cream scoop to measure out each latke, put into your hands and squeeze excess liquid. Form into a patty and place into the oil. Repeat this process. Cook each latke 2 to 4 minutes per side, until golden brown.
Allow to drain on a paper towel. Serve with crème fraiche or applesauce.