With olive burgers, the vegetal flavor of the olives plays a pleasing green note without the additional wateriness that comes from lettuce, and the salinity of the olive provides the only condiment I usually require with beef: salt. Also, unlike lettuce and tomato, sliced olives provide better traction between bun and burger, so there's no messy slippage: everything holds together well.
To figure out what fish are sustainable, we use information provided by Shedd or Monterey Bay Aquariums. During a recent visit to Fortune Fish in Bensenville, I found out that, alas, it's not all that easy to determine sustainability from pocket guides or apps.
Lydia Burns (cheesemonger at Marion Street Cheese Market) prepared for us one of the best versions of Caprese salad I can remember: just basil and tomato on bread…with Driftless, a sheep's milk cheese from Hidden Springs Creamery in Wisconsin.