Heat panini press or large skillet over medium heat.
Combine the creamy horseradish and mayonnaise together in a small bowl until fully incorporated.
To assemble sandwiches, spread softened butter on outside slices of bread.On the inside of a slice spread the mayonnaise mixture. Add half of the cheese, followed by the arugula and then pulled pork.Top it with remaining cheese and slice of bread with buttered side up.