Add cheddar, mayonnaise, caciocavallo, shallot, scallions, chile, salt, and garlic to corn; stir to combine. Spread butter on one side of each bread slice. Place 6 bread slices, buttered sides down, on a piece of parchment paper, and top evenly with cheese mixture (about 1/3 cup each); spread cheese mixture in an even layer. Top with remaining bread slices, buttered sides up.