Preheat oven to 350°F. Cut the croissants through the equator on a slight diagonal, leaving one side still attached. Fill each croissant with 2 ham slices and 1 cheese slice. Place 2 cashews in each sandwich so they poke out, pointing downwards like fangs. Transfer to a baking sheet lined with parchment paper; bake until cheese is melted, 10 to 12 minutes.