Preheat oven to 400 degrees.
In a small bowl, mix together all the Thousand Island ingredients.
For easy clean up, line a cookie sheet with foil. Place 24 cocktail rye on the cookie sheet in a single layer.
Spread each piece with 1 teaspoon of Thousand Island Dressing.
Place one piece of pastrami on top of each.
Add about 1 tablespoon of sauerkraut on top of that.
Add a small amount of dressing on top of the sauerkraut.
Top each with one piece of Swiss cheese.
Bake for about 8 minutes until cheese is melted. Place on a serving plate with a side dish of mustard, if desired, for dipping. Serve at once.