This charred scallion sauce is an ode to the classic French dish of leeks in vinaigrette, swapping out the leeks for tender charred scallions. It acts as a bright, addictive condiment for this quick-cooking cut of steak. If you can’t find hanger steak, skirt steak works for this recipe—adjust cook time accordingly. The sauce also pairs well with roast chicken, pork chops...we could do this all day.