1. In a small glass or stainless-steel bowl, combine the ginger, lemon juice, 1 tablespoon of the cooking oil, the sesame oil, 1/4 teaspoon of the salt, and the pepper. Set aside.
2. In a wok or a large nonstick frying pan, heat the remaining 2 tablespoons cooking oil over moderately high heat.
3. Add the garlic and cook, stirring, until fragrant, about 10 seconds. Add the bok-choy stalks and cook, stirring, for 1 minute. Add the snow peas and cook, stirring, for 1 minute. Add the radishes and the soy sauce and cook, stirring, for 1 minute longer.
4. Add the bok-choy leaves, the spinach, and the remaining 1/4 teaspoon salt to the pan. Cook, tossing gently, until the leaves just wilt, 1 to 2 minutes.
5. Add all but 1 tablespoon of the vinaigrette and toss to coat. Remove the vegetables from the pan.
6. In the same pan, heat the remaining tablespoon of vinaigrette over moderately high heat. Add the tofu and cook, turning occasionally, until warmed through, about 2 minutes. Return the vegetables to the pan and stir gently to mix.

Serves 4.