How to Make It
Shred potatoes and onion with the shredder blade in a food processor or on the big holes of a box grater. Place potato mixture in a large bowl; stir in juice, tossing well to combine. Place potato mixture in a colander; drain 15 minutes, pressing down on mixture occasionally with a wooden spoon. Using your hands, gently squeeze excess liquid from potato mixture.
Weigh or lightly spoon flour into a dry measuring cup. Place potato mixture in a large bowl; stir in flour, thyme, salt, and pepper, tossing well to combine. Add egg and egg yolk; stir well.
Preheat oven to 225°.
Line a baking sheet with paper towels. Add canola and olive oils to a 10-inch skillet over medium-high heat; heat until oil reaches 350°. Working in batches of 4, carefully drop potato mixture by 1/4-cupfuls into pan. Gently flatten with a spatula into 2 1/2-inch circles; cook 3 minutes on each side or until browned and crisp. Remove latkes from pan with a slotted spatula, allowing excess oil to drip back into pan. Place latkes in a single layer on prepared baking sheet. Place baking sheet in oven at 225° to keep latkes warm. Repeat procedure 3 times with remaining potato mixture, making sure oil temperature returns to 350° before adding mixture to pan. Serve with sour cream and applesauce, if desired.