Rinse the shredded potato in a large bowl of cold water. Drain and squeeze out excess water, then spread the potato out on a clean kitchen towel to dry completely.
In a large mixing bowl, mix together the potato, parsnip, chives, egg whites, cornstarch and 1 teaspoon of salt and 1 teaspoon of black pepper.
Heat half the butter and half the oil in a large frying pan over medium heat. Using about 2 Tbsp of potato mixture (squeezing any excess liquid out) form patties roughly 1 cm thick. Fill the pan with out crowding it. Press down on the latkes and cook on each side for about 3 minutes or until brown on the outside. Place on a paper towel and sprinkle with kosher salt. Add the remaining butter as needed. Serve with sour cream or apple sauce!