Grate the potatoes and onion into a large container. Add cold water to cover and the sour salt. Allow to rest for 5 minutes.
Drain the grated potatoes, squeezing out as much liquid as possible. Transfer to a bowl and add the eggs, flour, granulated onion, 2 teaspoons salt and 1 teaspoon pepper. Mix until well combined.
Add a small amount of oil to a griddle over high heat. Slide in the potato mixture in large oval-shaped spoonfuls. Cook for 3 minutes on each side. Cool in the refrigerator for 45 minutes.
Heat 2 inches of oil in a deep, heavy pot to 350 degrees F. In batches, fry the latkes for about 5 minutes, until brown and crisp. Drain on paper towels before serving.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy of Sherman's Deli & Bakery, Palm Springs, CA