To make the dressing: Put the soy sauce, vinegar, ginger, brown sugar, sesame oil, red pepper flakes, garlic and 2/3 cup of the olive oil into a blender. Blend until completely emulsified. Taste the dressing and adjust to your taste, adding more vinegar or sugar as needed. Pour half of the dressing into a jar and refrigerate for the salad.
Put the tofu cubes into a bowl and pour over the remaining dressing. Cover and refrigerate for at least an hour.
Remove the tofu from the dressing and pat dry. Heat the remaining 2 tablespoons olive oil in a nonstick skillet over medium-high heat. Cook the tofu on all sides until nicely browned and crisp, about 10 minutes. Toss in the sesame seeds and cook for another minute. Remove to a paper towel-lined plate.
To assemble the salad, put the mixed greens, halved tomatoes and sliced onion in a large bowl. Pour on half the remaining dressing, reserving the rest for later use. Toss to coat. Arrange the tofu and mandarin oranges all over the greens. Serve immediately.
Recipe courtesy of Ree Drummond