I came across a link to this photo of Tostadas with Ancho Grilled Cod in an Ask MetaFilter thread. The photographer added the briefest of instructions:
"Make the chips yourself by quartering tortillas and frying them in peanut oil. The corn slaw is just fresh corn and cabbage tossed with sugar and cider vinegar. For the cod - Marinate 30 minutes in olive oil, garlic powder, salt, and ancho chili powder. Grill over hot coals until just barely done and build as shown."
Using the link to the photo as a starting point I clicked around, as one does, until I found Jon Sullivan's website-- and more specifically his recipes. Not only do many of them beg to be tried, but each and every one includes photographs as mouth-wateringly beautiful as the one in this post.
This evening I decided to try to recreate Jon's dish. Obviously I had to wing it-- making up amounts and proportions as I went along. For the corn slaw I used half of a Napa Cabbage, two ears of corn, half a cup of cider vinegar and sugar to taste. For the cod marinade I substituted minced fresh garlic for the garlic powder and added a little Salsa de Jalapeño (from a very excellent guacamole recipe, also linked in an Ask MetaFilter thread) to give it some extra heat. I cooked the cod on a stove-top grill pan.
My tostadas weren't as pretty as Jon's, but they tasted mighty fine. The contrast of textures and taste impressions is a wake-up call as warm spicy fish segues to crunchy sweet slaw and tortillas while the burn of the Salsa de Jalapeño is soothed by the unctuous guacamole.