A loosely formed, juicy, flavorful patty, topped with melted tarentaise cheese and caramelized onions. Perfectly cooked. Well seasoned. The marrow's role wasn't evident at first glance (it's not like they put a huge glob of it on top of the burger patty), but it gives it a nice, rich taste that permeates. This burger should be eaten very, very slowly, as to really savor each bite. The pickles (standard bread and butter) and tomato (a big pale slice, maybe a little watery) were superfluous. The spicy aioli/mayo was a nice touch and contrasted well with the sweetness of the caramelized onions.
Sure, the surryano ham and housemade duck proscuitto were good, the pork rillettes were fine but nothing to write home about, and the foie gras torchon with cherry chutney was awesome, but the burger is what really stood out. Seriously delicious.