01 - In a large bowl, combine the chopped corned beef, sauerkraut, Swiss cheese, cream cheese, Dijon mustard, and black pepper. Mix until evenly blended.
02 - Roll the mixture into 1-inch balls and place them on a parchment-lined tray. Chill in the freezer for 20 minutes to firm up.
03 - Prepare a breading station: place flour in one shallow bowl, beat eggs in a second bowl, and place panko breadcrumbs in a third bowl.
04 - Coat each ball in flour, dip in egg, then coat thoroughly with panko breadcrumbs, ensuring even coverage.
05 - Heat 2 inches of vegetable oil in a deep skillet or saucepan to 350°F.
06 - Fry the balls in batches, turning occasionally, until golden brown and crispy, about 2–3 minutes per batch. Drain on paper towels.
07 - Whisk together mayonnaise, ketchup, pickle relish, horseradish, hot sauce, smoked paprika, garlic powder, salt, and pepper until smooth.
08 - Serve the Reuben balls warm with spicy Thousand Island sauce for dipping.