It's a cliche, it's terrible for you, and it's been featured on all those Food Network shows your sad shut-in aunt watches. And it's awesome. The recipe (if you can even call it that) is existentially simple: roast beef, a French baguette, au jus. The dip comes when the bread's dunked in the gravy; the French we're not sure of, although it makes the thing sound a lot fancier (read: worse) than it actually is. Philippe's has a homemade deli-style mustard with a bite that helps alleviate that "I'm just eating beef and bread!" feeling, which you'll need when you have the sandwich double-dipped. And you will do the doubledip. Trust.