Tofu, firm, drained, cut into 1-inch cubes

To marinate the tofu:

1. Combine the tofu, soy sauce, ginger, and garlic in a zip-close plastic bag. Squeeze out the air and seal the bag; turn to coat the tofu.

2. Refrigerate, turning the bag occasionally, about 20 minutes.

3. Drain the tofu and discard the marinade. Dry the tofu with paper towels and dust with flour, shaking off the excess.

To prepare the stir-fry:

1. (Ask an Adult for Help) Heat a nonstick wok or skillet over high heat until a drop of water skitters. Pour in the oil and swirl to coat the pan, then add the tofu, and stir-fry until lightly browned, about 2 minutes.

2. Transfer the tofu to a plate.

3. Add the scallion, ginger, and garlic to the pan and toss briefly.

4. Add the mixed vegetables, in batches if necessary, and stir-fry until tender, about 4 minutes.

5. Return all the vegetables to the pan (if cooking in batches). Add the tofu, and soy sauce; toss to combine. Stir in the sesame oil. Sprinkle with the toasted sesame seeds.