Gently whisk egg white in a small bowl and set it close to you.
Dice corned beef ad fine as you can, squeeze the juices out of the sauerkraut, and grate cheese if using a block.
Combine corned beef, Swiss cheese, sauerkraut, and some thousand island dressing in a mixing bowl and mix everything until it's evenly incorporated throughout.
Start preheating the oil to 350°F degrees over medium heat. Prepare a cooling rack by lining it with a couple of paper towels to soak up the excess oil.
To roll the egg rolls: Place egg roll wrapper on a diamond. Spread about 2 tablespoons of Reuben filling in a line, leaving about an inch on each side. Gently and carefully, fold the corner that's closest to you over the filling mixture, and tuck under the filling. Dip your fingers in egg white and run it all along the edges of the wrapper, this will help to seal the egg roll better. Fold both side corners toward center of wrapper, it will start to look like an open envelope. Carefully roll up the egg roll.
Repeat with remaining egg rolls while the frying oil is heating up.
Fry egg rolls in batches, don't over-crown the pot, until golden brown. Make sure to turn once the bottom side turns golden. (It will take 4-5 minutes to fry. If the egg rolls are getting dark too fast, the oil is too hot. On the other hand, if the egg rolls are not darkening fast enough, the oil is not hot enough. Keep oil temperature at 350° degrees.)
Use long metal tongs to take each egg roll out of the pot and onto the prepared cooling rack. Repeat until all egg rolls are cooked.
Serve with Thousand Island dressing for dipping.
Video
Notes
To air fry the egg rolls: Simply place them into the basket of your air fryer in a single layer, making sure there’s a little bit of space between each of them. Air fry the egg rolls at 390°F for approximately 9-11 minutes, turning half way through. (Preferred method for crispier egg rolls over baking!)
To bake: Place the egg rolls on a parchment paper covered baking sheet in one even layer and make sure to leave space between each egg roll. Preheat the oven to 425°F and bake for about 15 minutes, until they are deep golden brown.
Storing – Make sure to cool the egg rolls to room temperature first. Place a paper towel in the bottom of the food storage container and in between the layers. Keep refrigerated in the airtight container for 3-4 days.
Reheating – You can easily reheat the egg roll in the air fryer at 350°F for about 2 minutes. Your goal is to just crisp up the outside and heat through the inside. The air fryer is also the best method to get the outside crispy again.