Oh, and if you ever find yourselves in Central OK some places I highly recommend:
1. El Reno 20 miles west of OKC on I-40 is pretty much the birthplace. Sidís, where the above recipe came from is good, but I prefer the 75 year old Johnnieís Grill. They also have an Onion Burger festival in El Reno, which is pretty cool.
2. THE place in OKC is Nicís on Western. Unfortunately it is tiny and it was already hard to get in, and then Guy Fiere went and now it is almost impossible. There is ALWAYS a line out the door, but if you get lucky it is truly amazing.
3. My favorite local place was always little Bunnyís in NW OKC near Warr Acres. Cool little place and great onion burgers.