Bread: Spread butter onto one side of each slice of bread.
Assemble: Onto the other side of the breads, spread thousand islands dressing. Layer on half of the cheese, the Seitan Corned Beef, the sauerkraut, and the remaining cheese.
Cook: Cook over medium heat in a large skillet or panini press until outsides are golden brown and cheese has melted. Alternatively, set the oven to broil and cook for 3 to 5 minutes. Serve immediately.