Szechwan Seared Tuna with Soy-Mustard Sauce

2 tablespoons Dijon mustard
2 tablespoons soy sauce
2 and 1/2 tablespoons lime juice
1 tablespoon grated fresh ginger
6 tablespoons grapeseed oil
4 three-oz. pieces lean sushi-grade Ahi tuna
Salt, to taste
Coarsely cracked Szechwan pepper, to taste
2 oz. mixed baby greens

In a bowl, whisk mustard, soy sauce, 2 tablespoons lime juice, ginger,
and shallot. In a steady stream, add 4 tablespoons oil, whisking
constantly until blended. Season tuna with salt and pepper. In a fry
pan over high heat, warm 1 tablespoon oil until nearly smoking. Add
tuna and sear, about 30 seconds per side. Immediately remove from pan.
In a bowl, combine greens, remaining tablespoons of oil, remaining
lime juice, and salt. Toss to mix and divide among four salad plates.
Slice tuna into 1/4-inch thick slices and divide among plates, fanning
sliced next to salad. Drizzle 1 tablespoon soy mustard over each
serving, and serve immediately. Serves 4.