This burger defies classic burger rules: The bun is deliberately soggy and the cheese is Gruyere instead of the mainstay American. It's really like a French onion soup hamburger. What kinds of meat? I choose an 85/15 blend if I buy pre-ground at the supermarket. If I have a butcher grind for me, I like sirloin and short rib, about equal parts. You could also get away with this burger on some deeply toasted sourdough bread in place of the buns…