Lightly brush pineapple rounds with oil. Heat a grill, or grill pan, to medium high heat. Place pineapple rounds on grill and cook until golden brown. Gently flip rounds and continue to cook until golden brown on both sides. Set aside.
Place bread slices on a clean work surface. Spread the Spicy Honey Mustard over four slices of bread. Evenly divide the ham over the mustard. Top each with 2 pineapple rounds and a slice of cheese. Finish with another slice of bread. Butter each outer side of bread.
Saute sandwiches over medium heat until golden brown on both sides and the cheese is melted (a Panini maker can also be used). Cut sandwiches in half and serve.