There's this east coast burger chain I really like called Zinburger. It's more of the sit down restaurant kind of deal than a fast food joint but the burgers are honestly the best I've ever had. At least the one by me is, can't speak for the other locations. Their French Dip burger is bomb; ground prime rib, Parmesan horseradish sauce, melted provolone and a big ol' stack of fried onions. All those salty and savory flavors pair so well with the sweet au jus.