First, set your oven temperature to 375 degrees Fahrenheit (190 degrees Celsius).
Mix the sauerkraut and thousand island salad dressing in a bowl. Take the crescent roll dough, split it in two, then place one half onto a floured work surface and pinch closed to make 1 sheet. Roll that to about 12 inches square before fitting it into the baking sheet. Do the same for the other half, rolling it to 9 inches square and setting it aside.
Precook the dough crust in the baking dish in the oven until it acquires a light brown shade, typically taking around 8 to 10 minutes. Once removed from the oven, arrange four cheese slices at the bottom of the crust. Place the corned beef on the cheese slices, then spread the sauerkraut mixture. Add another layer of four Swiss cheese slices to the sauerkraut mixture. Take the second sheet of crescent roll dough and carefully position it onto the filled baking sheet, ensuring the top crust is pressed down onto the edges of the dish to create a seal. Finish by applying a coating of beaten egg white using a brush.
And finally, place the dish in the oven and bake it for 15 to 20 minutes, or until the cheese has melted and the crust has become golden brown. Once done baking, allow it to rest for approximately 5 minutes before slicing.