Take the cheese slices and cut them in half diagonally.
Cut the hanpen in half diagonally. With a sharp knife, carefully cut a slit into the long edge of the triangle to form a pocket. Fit two slices of cheese into the pocket. Repeat with the other half of hanpen.
In a small pan over medium heat, melt the butter. Add the stuffed hanpen. Sear until golden brown on one side. Add the garlic and stir around. Turn the hanpen over and sear the other side until golden brown and the cheese is melted. Transfer to a serving plate. Serve immediately.