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Blackened Ahi with Soy-Mustard Sauce

Slices of blackened ahi tuna with soy-mustard sauce lined up next to each other with two lime wedges on the side.
Blackened ahi with soy-mustard sauce is Hawaiian meets Creole, with tender tuna being seared in fragrant spices. Served with an indulgent beurre blanc, it's one of Chef Roy Yamaguchi's signature fusion dishes.
Roy Yamaguchi

Prep 35 mins
Cook 3 mins
Total 1 hr
4 servings
471 kcal


For the soy-mustard sauce

  • 1/4 cup mustard powder preferably Colman’s
  • 2 tablespoons hot water
  • 2 tablespoons rice wine vinegar
  • 1/4 cup soy sauce

For the beurre blanc

  • 1/2 cup dry white wine
  • 2 teaspoons white wine vinegar
  • 1 teaspoon fresh lemon juice
  • 1 tablespoon minced shallot
  • 2 tablespoons heavy cream
  • 1 stick (4 oz) cold unsalted butter chopped
  • 1/4 teaspoon salt
  • Freshly ground white pepper

For the blackening spice

  • 1 1/2 tablespoons paprika
  • 1/2 tablespoon cayenne pepper
  • 1/2 tablespoon pure chile powder
  • 1/4 tablespoon freshly ground white pepper
  • 1/2 tablespoon ground sandalwood optional

For the tuna

  • 8 ounces ahi tuna fillet* about 2 inches thick and 5 inches long
  • 2 tablespoons olive oil
  • 3/4 cup warm Beurre Blanc

For the garnish

  • 2 to 3 tablespoons pink pickled ginger
  • 1 ounce daikon sprouts
  • 1/2 tablespoon black sesame seeds toasted
  • Lime wedges (optional)


Make the soy-mustard sauce

  • Mix the mustard powder and hot water together in a cup to form a paste. Let sit for a few minutes to allow the flavor and heat to develop. Add the vinegar and soy sauce, mix together, and pass through a fine-mesh sieve into a bowl. Cover and refrigerate for at least 1 hour to allow the flavors to develop.

Make the beurre blanc

  • Combine the wine, vinegar, lemon juice, and shallot in a heavy stainless steel saucepan. Bring to a boil over medium-high heat and cook to reduce the liquid until it becomes syrupy.
  • Add the cream and cook to reduce by half. Decrease the heat to low and gradually add the butter, stirring slowly; do not whisk. Take care not to let the mixture boil, or it will separate. When the butter is incorporated, season with salt and pepper to taste, and strain through a fine-mesh sieve into the top of a double boiler. Keep warm over barely simmering water.

Make the ahi

  • Mix all of the blackening spice ingredients together on a plate. Dredge the ahi in the spice mixture on all sides.
  • Heat the olive oil in a nonstick skillet over high heat and sear the ahi for 15 to 30 seconds on each side for rare, 1 minute on each side for medium-rare, or to the desired doneness. Remove the ahi and cut into 20 thin slices.
  • For each serving, arrange 5 slices of ahi in a fan, pinwheel, or cross shape on the plate. Spoon or drizzle a little of the Soy-Mustard Sauce around the tuna, and then spoon or drizzle the Beurre Blanc around.
  • To garnish, arrange a small mound of the pickled ginger next to the fish and top with the daikon sprouts. Sprinkle the sesame seeds over the Soy-Mustard Sauce and, if desired, add some lime wedges.


*What can I substitute for ahi tuna?

Not to sound dictatorial but…this recipe really works best with Chef Roy Yamaguchi’s recommendation of ahi tuna. In North America, both yellowfin and big-eye tuna are often marketed as ahi (the Hawaiian word for yellowfin), so if this is what find—you have nothing to worry about. Australian bonito or skipjack tuna may be substituted if they’re really, really fresh.