California Ahi Tuna Sandwich

Ingredients

Equipment Needed

• •12-inch cast iron skillet or heavy-bottomed pan
• •Very sharp slicing knife
• •Shallow plate or dish for sesame coating
• •Instant-read thermometer (optional)

Instructions

1. 1

   Prepare the tuna

   Remove the tuna from the refrigerator fifteen minutes before cooking. Pat it completely dry with paper towels on all sides. Moisture is the enemy of a proper sear. The fish should feel tacky to the touch, not slick. Trim any dark bloodline portions, which taste metallic when seared.

   If your tuna block is uneven in thickness, slice it into two pieces of similar height. Uniform thickness ensures even cooking.
2. 2

   Create the sesame crust

   Combine white and black sesame seeds on a plate or shallow dish. Mix in the salt and pepper. The contrast of colors isn't just beautiful; white sesame seeds toast faster and will tell you when to flip. Roll the tuna block in the sesame mixture, pressing firmly on all sides until completely coated. Every surface should wear a dense layer of seeds.

3. 3

   Make the wasabi mayo

   Whisk together the mayonnaise, wasabi paste, soy sauce, and lime juice in a small bowl. Taste it. The heat should announce itself clearly but not dominate. Add more wasabi if you want more fire. The lime brightens everything and keeps the mayo from tasting heavy. This can be made up to three days ahead.

   Real wasabi is rare and expensive. Prepared wasabi paste works fine here, and its horseradish base actually holds its heat better than true wasabi, which fades quickly.
4. 4

   Prepare the avocado

   Halve the avocados and remove the pits. Score the flesh in a crosshatch pattern while still in the skin, then scoop out with a large spoon. You want thick slices, not mush. A ripe avocado yields to gentle pressure but doesn't feel hollow or stringy. Drizzle the slices with a little lime juice to prevent browning.

5. 5

   Toast the rolls

   Split the ciabatta rolls and spread the cut sides with softened butter. Toast them in a dry skillet over medium heat or under a broiler until golden and crisp, about two minutes. You want a surface sturdy enough to hold the components without becoming soggy. Set aside, cut side up.

6. 6

   Sear the tuna

   Heat a cast iron skillet over high heat until a drop of water vaporizes on contact. Add the neutral oil. When it shimmers and just begins to smoke, lay the tuna in the pan. Do not move it. Sear for thirty seconds, until the sesame seeds turn golden on the bottom and you see about an eighth-inch of cooked flesh creeping up the sides. Flip and sear the other long side for thirty seconds. Sear each narrow end for fifteen seconds if your block has significant depth.

   The tuna will continue cooking from residual heat after you remove it. Pull it when the seared band is narrower than you think it should be.
7. 7

   Rest and slice

   Transfer the seared tuna to a cutting board. Drizzle all sides with toasted sesame oil while still warm. Let it rest for two minutes. Using your sharpest knife, slice the tuna against the grain into pieces about a third of an inch thick. The interior should be ruby red, cool to the touch, the seared exterior a narrow band of tan surrounding that jewel-toned center.

8. 8

   Assemble the sandwiches

   Spread wasabi mayo generously on both cut sides of each roll. Arrange avocado slices on the bottom half, slightly overlapping. Shingle tuna slices over the avocado, four or five slices per sandwich. Add a small mound of pickled ginger if using. Pile peppery greens on top, enough to provide crunch in every bite but not so much that the sandwich becomes unwieldy. Close with the top half, press gently, and slice on the diagonal.

Chef Tips

• •Buy your tuna from a fishmonger who specializes in sushi-grade fish, or from a Japanese market. Supermarket tuna labeled 'sushi-grade' is often marketing rather than fact. Ask when it was cut. The fish should be ruby red with no browning.
• •The bread matters more than people admit. Ciabatta has the structure to hold up to the moist components without collapsing. Soft sandwich bread turns to paste. Portuguese rolls from a good bakery work beautifully, as do properly crusty French rolls.
• •For transporting these sandwiches, wrap them tightly in parchment paper, then foil. Keep in a cooler with ice packs. Assemble without the greens, which go in a separate container and get added just before eating to prevent wilting.
• •If making sandwiches ahead for a gathering, sear and slice the tuna up to two hours in advance. Keep it refrigerated on a plate, covered with plastic wrap pressed directly onto the surface. The fish will be cold rather than cool, but the quality holds.

Advance Preparation

• •Wasabi mayo can be made up to three days ahead and refrigerated. The flavors meld and improve with time.
• •Sesame seed mixture can be combined and stored in an airtight container for up to one month.
• •Toast the rolls up to four hours ahead. Store at room temperature, wrapped loosely in a kitchen towel.
• •The tuna must be seared fresh. Do not sear ahead and refrigerate; the texture becomes rubbery and the sesame loses its crackle.

Frequently Asked Questions

Nutrition Information

1 serving (about 370g)