2 tablespoons capers, rinsed, drained and patted dry
1 teaspoon lime zest (grated lime peel)
Juice of 1 lime
Ground white pepper to taste
In a food processor fitted with a medium shredding disk, or using a box grater, shred the potatoes and onion into a large mixing bowl. With a wooden spoon, stir in the salt, lemon juice and potato flakes until well combined. Add mayonnaise, crab, egg and egg white, paprika, horseradish and white pepper; stir well.
Transfer mixture to a colander and place over a bowl. Cover mixture with plastic wrap and put colander and bowl in the refrigerator to drain and chill for 20-30 minutes, or up to 4 hours. Meanwhile, prepare Caper-Lime Sauce. To make sauce, combine all the ingredients and whisk well; refrigerate until serving time.
When potato-crab mixture is chilled, form it with clean hands into about 8 cakes, each approximately 1/2 inch thick and 4 inches in diameter. In a large, heavy skillet, over medium-high heat, heat 2 tablespoons of the oil. When moderately hot, cook 4 of the potato cakes until golden brown on the bottom and release easily from the pan. Flip cakes and cook on second side until well browned and cooked through. Transfer cakes to paper towels to drain. Add the remaining tablespoon of oil and cook the remaining cakes. Serve cakes with the Caper-Lime Sauce.