If using uncooked rice, start it first according to package instructions.
Press tofu between paper towels for 5 minutes while chopping vegetables.
Mix sauce ingredients in a small bowl until cornstarch dissolves completely.
Heat oil in wok over high heat (400°F/204°C).
Cook tofu cubes until golden, about 5 minutes, stirring occasionally to ensure even browning.
Add vegetables, starting with the firmest (carrots, broccoli), cooking for 2-3 minutes.
Add bell peppers and snap peas, cooking for another 2 minutes.
Add garlic and ginger, stir-fry for 30 seconds until fragrant.
Pour sauce over mixture, stir constantly until thickened, about 2 minutes.
Add water chestnuts and baby corn if using, heat through.
Serve over rice, garnished with green onions and sesame seeds.