In a small saucepan, heat sauce over medium heat until hot; set aside.
Preheat an electric sandwich press or covered indoor grill.
To assemble sandwiches, spread both sides of each bread slice with butter. Place bread slices, a few at a time, in the sandwich press or indoor grill. Cover and cook about 4 minutes or until bread is toasted, turning if necessary.
Immediately after bread is toasted, spread 3 tablespoons sauce on half of the bread slices. Top with some of each of the cheeses and the remaining bread slices. Return to sandwich press and grill 3 to 4 minutes more or just until cheese melts. Serve with remaining sauce for dipping.
