In a small saucepan, heat the turkey gravy over medium heat until warmed through. Stir occasionally to prevent sticking. Season with salt and pepper to taste.
While the gravy is heating, butter one side of each slice of bread.
In a skillet over medium heat, place two slices of bread, buttered side down. Layer each with a slice of Swiss cheese, followed by half of the turkey, and then another slice of Swiss cheese.
Top each sandwich with another slice of bread, buttered side up. Cook for about 3-4 minutes, or until the bottom is golden brown.
Carefully flip the sandwiches and cook for another 3-4 minutes until the other side is golden brown and the cheese is melted.
Remove the sandwiches from the skillet and cut them in half. Place on plates and ladle warm turkey gravy over the top.
Garnish with chopped parsley if desired and serve immediately.