Croquettes typically feature a meat or mashed potato filling mixed with bechamel sauce, covered in breadcrumbs, and then fried until crisp and golden. This recipe for Tuna Croquettes features a creamy tuna filling that is seasoned with nutmeg and then covered in a breadcrumb mixture and fried in oil until golden, true to traditional croquette form. Refrigerate the tuna filling mixture before shaping and covering in breadcrumbs to ensure the croquettes hold their shape when frying.