To make Russian Dressing- In a small bowl whisk together mayonnaise, onion, horseradish, Worcestershire sauce, parsley, chili sauce, and ketchup until smooth. Chill before serving.
Butter one side of 4 slices of bread. Place them buttered side down on a sheet of wax paper. Top each with a slice of Swiss cheese; divide half of the corned beef among them. Squeeze out any moisture from the sauerkraut. Divide the sauerkraut among each of the sandwiches. Top the sauerkraut with 1-2 tablespoons of Russian dressing on each sandwich. Add another layer of corned beef and top with another slice of Swiss cheese on each sandwich. Butter the side of the sandwich facing up.
Pre-heat a large skillet to medium heat. Cook the sandwiches on one side until golden brown. Use a spatula to flip the sandwiches over and finish cooking on the other side until golden brown. Cut in half and serve.