With a bit of research and social engineering, an enterprising burger enthusiast has figured out the recipe for the infamous Shake Shack burger.
Exclamation point interlude: !!!!!!!!!!!!!
Upon tasting it, my immediate thoughts are mayo, ketchup, a little yellow mustard, a hint of garlic and paprika, perhaps a touch of cayenne pepper, and an elusive sour quality that I can't quite pinpoint. It's definitely not just vinegar or lemon juice, nor is does it have the cloying sweetness of relish. Pickle juice? Cornichon? Some other type of vinegar? I can't figure it out. This was going to take a little more effort.
Totally doing this for dinner one of these nights. We'll probably cheat on the ground beef...we've got some Pat LaFrieda patties stockpiled in the freezer.