Preheat the oven to 350 degrees. Coat a small baking dish with cooking spray.
Line a baking sheet with parchment paper.
Place the cut dark rye bread pieces on the baking sheet. Place into the oven and bake for 5-7 minutes, or until crisp. Remove from the oven; set aside.
Combine the cream cheese, sour cream, mayonnaise, ketchup, and relish together in a large bowl; mix until creamy and well combined.
Add the Swiss cheese, Pastrami, sauerkraut, Gruyere, and fresh parsley; mix until well combined.
Pour into prepared baking dish. Place into the oven and bake for 15-20 minutes, or until bubbly.
Serve immediately with dark rye crostini. Enjoy.