These were a big hit, even though I didn't follow the recipe exactly as posted. I did not include the breadcrumbs, as I don't like filler in my burgers. I also omitted the sun-dried tomatoes (because I thought I had some, and I didn't). Made on the outdoor grill, these burgers were very flavorful and juicy. The horseradish mayo was a really nice touch. We made some with cheddar (because some people simply have to have a cheeseburger). Garnished with a nice heirloom tomato slice and red onion. Thanks for sharing! Made for Fall PAC 2011.