Unfold the thawed puff pastry sheet onto your counter. You can lightly flour the surface, or roll out onto a piece of parchment paper like I do. Lightly roll to flatten creases, without making it any larger.
Brush with egg wash. Reserve egg wash.
Mix together cream cheese and Thousand Island Dressing, spread over puff pastry.
Top with corned beef, sauerkraut and Swiss cheese.
Roll toward you "jelly roll" style. Wrap in plastic wrap and place in the fridge for a couple of hours.
Preheat oven to 400 degrees. Remove plastic wrap and slice roll into 20 1/2" pieces. Place on parchment lined baking sheet. Brush tops with reserved eggwash.
Bake for 15 minutes -- serve warm or room temperature with Homemade Thousand Island Dressing.