I use portabella mushrooms (also known as Agarics bisporus) instead of hamburger buns when having a burger. I will warn you that they are messy! But at twenty-two calories per hundred grams and no fat I can deal with the mess. And I don't feel as guilty as I should that there is bacon and cheddar cheese hiding in the middle of that burger. Shhh, our secret.
To add to the mess factor I dress one side of the "bun" with dijon mustard and the other with snap pea coconut chutney. Oh my! That chutney is so de-lish, I could eat it by the spoonful. The chutney is thanks to KarenFood. You might know her as a regular visitor on CBC Radio with Terry McLeod on the weekends. But I digress, if you're in the Winnipeg area you just might be lucky enough to pick up some Snap Pea and Coconut Chutney at the Hydro Building's downtown Farmers Market on Thursdays.