Peel the potatoes and place in a bowl with enough water to cover them so they won't brown. Let sit in water for 5 minutes. When ready to prepare, drain the potatoes in a colander.
Using a food processor with a grating disc, grate the potatoes and onions. Place potato and onion mixture in a clean dish towel, wrap tightly and squeeze hard to remove the liquid. Transfer to a large bowl.
Add the corned beef, eggs, flour, baking powder, salt and black pepper to potato mixture and mix until flour is absorbed.
Preheat oven to 250°F and place a wire rack on top of a baking sheet. Pour in about ¼ inch of oil into a large skillet and heat over medium-high heat. Scoop up ¼ cup of the mixture per fritter and drop into skillet. Use a spatula to flatten into discs. When the edges of the fritters are brown and crispy, about 3-5 minutes, flip. Cook for another 3-5 minutes or until browned.
Transfer cooked fritters to a paper towel-lined rack to drain and then put on wire rack in oven to keep warm while you cook the remaining fritters. Serve with some sour cream.
Notes
Soak the potatoes in water for 5 minutes so they don't brown. However don't soak too long or you'll remove the starch.
Place the potatoes and onion in a dish towel and tightly squeeze to remove the excess liquid which helps create the crispiness you want.
Use a large cookie scoop so you can get uniform size fritters.
Once you add the fritter mixture to the oil, don't move them for 3-5 minutes before flipping so they create a crispy exterior.