This cool, elegant, Japanese inspired appetizer is great in the summer, especially if you have cucumbers, sweet red onions, and chiles fresh from your garden (or from your favorite farmer's market). For an hors d'oeuvre party you could serve the tuna on crackers, such as the Crispy Sesame Crackers in the Mustards Grill Napa Valley Cookbook. And of course you could feature as presented below in any small plates meal.

In takes a bit of time for the cucumber to "weep," and the wasabi paste needs to sit at least 30 minutes before being used, but everything can be done ahead of time. Then final assembly will just take a few minutes.

Wasabi is a Japanese horseradish. For this dish, we mix wasabi powder with water to make wasabi paste. You could buy a tube of ready-mixed wasabi paste instead, though you should check the label to see if it has been loaded up with additives. Wasabi powder and paste are both easy to find at Asian markets (or well stocked supermarkets). If you're really lucky, you might find fresh wasabi roots, and could try grating your own paste. Fresh wasabi roots are much smaller than Western horseradish roots, dark brown on the outside, and bright light green inside.

12 ounces sushi grade tuna

Wasabi Paste:
2 tablespoons wasabi powder
1/4 to 1/2 cup water

Cucumber Salad:
1 English cucumber, unpeeled, sliced paper thin
2 jalapeño chiles, stemmed, seeded, and julienned
1/2 medium red onion, thinly sliced
2 tablespoons rice vinegar
2 tablespoons extra-virgin olive oil

San Bai Su Drizzle:
1/4 cup mirin or sake
1/4 cup tamari or soy sauce
1/4 cup rice vinegar
1/4 cup mirin or sake

12 slices avocado
2 tablespoons toasted sesame seeds

Spread the cucumber slices over a baking sheet and sprinkle them with the kosher salt. Let them sit for 30 minutes to draw out the excess moisture. Combine the chiles, onion, rice vinegar, and olive oil in a mixing bowl large enough to hold the cucumbers, and keep refrigerated until needed. After 30 minutes, pat the cucumbers dry with paper towels and toss them into the bowl with the chiles and onions.

Mix the ingredients for the San Bai Su Drizzle together in a small bowl. Chill 6 medium plates in the fridge.

To Serve:
Drizzle the chilled plates with some of the wasabi paste, then gently measure out 1/3 cup portions of the tuna and turn them out onto the center of each plate. Place 3 mounds of cucumber salad about, and Drizzle with San Bai Su. Cross 2 slices of avocado on top of each portion of tuna, and sprinkle the sesame seeds over all.

* NOTE
Because the tuna is going to be served raw, it's very important to buy the best quality. If you're buying ahi, it should be deep red, not a cherry red or candy apple look that is achieved by gassing the fish with carbon monoxide. You definitely don't want that. Pass it up if the blood line is brown rather than red, or if the flesh has soft spots or dimples. Albacore tuna is lighter in color, but equally delicious. For both, look for clear, firm flesh with a clean, fresh smell. Tell your fish purveyor you're serving the tuna raw, and you want sushi -- or grill-grade tuna.