Place the Yukon Gold potatoes in a large pot of boiling salted water and simmer for 15 to 20 minutes, until very tender when tested with a knife. Drain and pass through a ricer or the coarsest blade of a food mill into a large bowl and set aside.
Grate the Idaho potatoes lengthwise in long shreds, either by hand or in a food processor fitted with the coarsest grating disk. Place the potatoes on a kitchen towel, squeeze out most of the liquid, and transfer to the bowl with the cooked potatoes. (Don’t worry—they’ll turn pink.) Grate the onion either by hand or in the food processor and stir into the potatoes along with the eggs, panko, chives, 2 teaspoons salt, and 1 teaspoon pepper.
Heat 2 tablespoons of butter with 1 tablespoon of olive oil in a large (12-inch) sauté pan over medium-high heat, until sizzling. Drop heaping tablespoons of the potato mixture into the skillet (you want them to be messy). Flatten the pancakes lightly with a metal spatula and cook for 2 to 3 minutes on each side, until browned. Continue adding butter and oil, as needed, to fry the remaining batter. Serve hot with sour cream and chives.
Prepare the mixture and refrigerate for several hours. Fry just before serving or up to 30 minutes ahead. Place on a sheet pan, and reheat at 400 degrees for 5 to 10 minutes.
Copyright 2016, Cooking for Jeffrey, Clarkson Potter/Publishers, All Rights Reserved