Charred Tuna, Mizuna & Pear with Black Vinaigrette

Double the portion and call it dinner.  The alluring vinaigrette here is made with Chinese black vinegar and further darkened with soy sauce.  A slice of fresh sweet pear, warmly slightly under the fish, is a radical jolt of pleasure.  I might try it soon with thin slices of peach.

1/4 cup Chinese black vinegar
1/4 cup soy sauce
4 teaspoons honey
4 teaspoons extra-virgin olive oil, plus more for the tuna
1-1/4 teaspoons Asian sesame oil
1/2-inch piece peeled fresh ginger
1 medium garlic clove
2 thick tuna steaks, 9 to 10 ounces each
3 cups Asian greens, including mizuna
1 medium ripe Bartlett or Asian pear (or peach), thinly sliced
2 tablespoons toasted sesame seeds

Mix the vinegar, soy sauce, honey, olive oil, and sesame oil in a bowl; stir until the honey dissolves.  Grate the ginger and garlic on a Microplane grater; add to the dressing.  Halve the tuna fillets (you want 4 thick pieces) and coat lightly with olive oil and salt.  Heat a large nonstick skillet until hot.  Add the tuna sear 2 minutes on each side.  Keep the tuna very are.  Divide the greens among 4 shallow bowls or plates and top with portion with 2 pear slices.  Drizzle with some of the dressing.  Cut the tuna into thick slices; arrange atop the salads, overlapping slightly. Drizzle dressing on tuna and greens and sprinkle with sesame seeds.  Serves 4