Tuna Tostadas with Chipotle Mayo, Avocado and Crispy Leeks (Contramar Style) - Rick Bayless

Ingredients

• 6 thin store-bought corn tortillas, preferably 4 to 5 inches in diameter (ones that are stale—at least not moist—are best)
• 1 leek (white part only), roots cut off, cleaned, cut into rings about 1/8 inch thick
• Oil for frying to a depth of 1 inch
• Salt
• 8 to 10 ounces sashimi-quality tuna, preferably a slab about 4 inches square and 2 inches thick (tuna belly is often the right thickness)
• 2 tablespoons soy sauce
• 2 tablespoons fresh orange juice
• 1/4 cup best-quality mayonnaise (see note above)
• About 1 tablespoon finely chopped canned chipotle chiles en adobo
• 1 avocado, cut in half, pit removed, flesh scooped from skin and cut into 12 slices
• 1 lime, cut into six wedges