If you can find bison flank steak, it is much more lean than beef and has a more delicate flavor, but beef flank works perfectly in this recipe too. Chef Rucker paired his flank steak with an Argentinian chimichurri that begins traditionally, with parsley and oregano, but also includes the novelty of mint and feta cheese for fresh and creamy notes. Dab this classic condiment on grilled chicken, fish, and vegetables, too.