To prepare the Soy-Mustard Sauce, mix the mustard powder and hot water together 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 strain through a fine sieve. Chill in the refrigerator.

Warm the Beurre Blanc in a double boiler (see below for recipe).

Mix all the blackening spices together on a plate, and dredge the Ahi covering all sides. Heat a lightly oiled cast-iron skillet and sear the Ahi over high heat to the desired doneness (about 15 seconds per side for rare to 1 minute per side for medium-rare). Cut into 16 thin slices.

For each serving, arrange 4 slices of the Ahi in a pinwheel or cross shape on the plate. Ladle a little of the Soy-Mustard Sauce in two opposing quadrants between the tuna, and ladle the Beurre Blanc in the other two quadrants. To garnish, put a small mound of the red pickled ginger on the Beurre Blanc on either side, and sprinkle the sesame seeds over the Soy-Mustard Sauce. Arrange the spice sprouts, bell pepper, and cucumber at the very center of this pinwheel.

Beurre Blanc Sauce
Yield: About 1-1/2 cups

The foundation for many of my sauces is this wonderfully adaptable sauce, otherwise know as White Butter Sauce.

1/2 cup white wine
2 teaspoons white wine vinegar
1 teaspoon fresh lemon juice
1 tablespoon minced shallot
2 tablespoons heavy cream
1/2 cup unsalted butter, chopped
1/4 teaspoon salt
Freshly ground white pepper to taste

Combine the wine, wine vinegar, lemon juice, and shallot in a saucepan and bring to a boil over medium-high heat. Reduce the liquid until it becomes syrupy. Add the cream, and reduce by half. Turn the heat to low and gradually add the butter, stirring slowly (do not whisk) until it is all incorporated. Be careful not to let the mixture boil, or it will break and separate. Season with salt and pepper and strain through a fine sieve. Transfer to a double boiler and keep warm.