Sauce

1 lemon
1 lime
1 orange
4 tablespoons rice vinegar
4 tablespoons soy sauce
4 tablespoons sugar
1 to 3 small Thai chiles
4 sprigs of rosemary, basil, or other herb (for garnish)

Halve the lemon, lime, and orange and use a grapefruit knife to remove the seeds and cut the pulp from the skin. Be careful not to include any of the white pith. Discard seeds and skins. In a blender manually pulse the citrus pulp and the other ingredients until thick but not finely puréed. (Alternatively, you can squeeze the citrus fruits and use only the juice, not the pulp, but the sauce will be thinner.) Set aside and keep at room temperature.

Tuna

1/4 cup white sesame seeds
1/4 cup black sesame
4 six-ounce pieces thick-cut ahi tuna steaks
kosher salt and pepper to taste
2 teaspoons peanut oil (for frying)

Mix sesame seeds together in a shallow pan. Season the ahi with salt and pepper, then dredge in the sesame seeds, pressing the seeds into the fish so they stick. In a large sauté pan or a wok heat the peanut oil until almost smoking. Sear the tuna steaks for about 30 seconds on each side; the center should stay rare. Remove from pan and whip out any burned sesame seeds in preparation for cooking the broccoli.

Broccoli

2 tablespoons peanut oil
1 teaspoon peeled and finely chopped ginger
1 teaspoon finely chopped garlic
1 tablespoon thinly sliced scallions
2 bunches Chinese broccoli (may substitute rapini), florets only
2 tablespoons sake
2 tablespoons soy sauce
pinch black pepper

Turn heat to high and add the peanut oil to the same pan used for cooking the tuna. When the oil is hot, stir in the ginger, garlic, and scallions. Add the broccoli and quickly toss to coat with the seasoned oil. Add the sake and the soy sauce, season with a pinch of black pepper, and cook for approximately 1 minute. Remove from heat.

Crispy Sweet Potatoes

1 medium sweet potato, peeled
2 cups peanut oil (for frying)
kosher salt to taste

In a deep saucepan heat the oil to 350 degrees. Using a vegetable peeler, cut the yam in long, skinny strips until you are left with just the center core, which you discard. Fry the strips, stirring constantly until lightly browned, 3 or 4 minutes. Drain on a paper towel and season with salt.

To serve, arrange the stir-fried broccoli in the middle of a plate. Slice each ahi tuna steak 1/2-inch thick and arrange the slices over the broccoli. Drizzle the fish and plate attractively with the citrus soy sauce and garnish with crispy sweet potato strips. Serves 4.