Place all of the bread slices flat on a cutting board and generously spread one side of each slice with butter. Flip the bread slices and spread the unbuttered sides with honey and layer 4 of the slices with cheese and ham. Top ham with mango, apples and red onions. Cover with remaining bread slices, buttered side out. Place a large skillet over medium heat and melt 1 tablespoon of remaining butter in the skillet, swirlling around to coat the skillet. Transfer the sandwiches to the skillet with a spatula and cook until golden brown. Turn the sandwiches and add remaining butter to the skillet. Cook until the cheese is melted and the second side is golden brown. Remove the sandwiches from the skillet and place on a plate. Cut into halves and serve.