Mix all the marinade ingredients in a small bowl. Whisk well, keep aside.
Place the tofu pieces in a large bowl. Pour the marinade over it and gently toss and coat well.
Keep aside for 15 minutes at least and up to one hour in the refrigerator.
Meanwhile chop the bell pepper into long strips and the onion into thin slices or cut into quarters and peel each quarter into petals (like you see in the photo of the dish).
Mix the 2 tsp corn flour, 1 tbsp soy sauce, 1/4 cup water to make a slurry, in a small bowl. Keep aside.
Place a wok on HIGH heat with the oil. Once the oil is hot, quickly stir in the green chillies, ginger garlic. Don't brown the garlic. Add the sliced veggies and stir fry on high flame for 5 minutes or so, with constant stirring, so it doesn't burn.
Next drain the marinated tofu and add it to the wok, toss it gently on medium flame for 2-3 minutes.
Add the leftover marinade plus the slurry and toss until it gets a well glazed look. Add the 1 tsp rice vinegar, give it a final stir and remove into a bowl.
Garnish with finely chopped coriander or spring onion batons and toasted sesame seeds.
If you want to serve with rice, use an extra tsp of cornflour and increase water to around half cup, simmer until a little thick, adjusting the seasoning accordingly.