#### 1. Preheat the oven:

Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish or line it with parchment paper.

#### 2. Prepare the bottom layer:

Unroll one can of crescent roll dough and press it evenly into the bottom of the prepared baking dish, pinching the seams together to create a solid layer.

#### 3. Layer the filling:

Spread the Thousand Island dressing over the crescent dough. Layer the corned beef evenly, followed by the sauerkraut. Drizzle with Dijon mustard and sprinkle the shredded Swiss cheese on top.

#### 4. Add the top layer:

Unroll the second can of crescent roll dough and lay it over the filling, pinching the seams together. If desired, brush the top with the beaten egg for a golden crust.

#### 5. Bake:

Bake in the preheated oven for 25–30 minutes, or until the crescent dough is golden brown and cooked through.

#### 6. Cool and serve:

Let the bake cool for 5 minutes before slicing into squares. Serve warm.