Drain any excess water from the tofu by pressing it. Break them up into small chunks.
Cut red bell peppers into squares.
Add all the ingredients for the batter into a bowl and mix them. Add 1/4 cup of water to get a smooth and thick paste. Add more if required.
Add the tofu chunks into the mixture and coat evenly. You can coat them one by one too.
Heat up some oil to fry. Fry until golden and crispy and drain the excess oil with a paper towel.
In a wok or large pan, heat 2 tablespoons of oil over medium-high heat.
Add the minced ginger, chillies (if using) and white part of scallions. Sauté for a minute until fragrant.
Add the soy sauce, vinegar, sriracha, sweetener, and salt (if needed). Mix well. Add chili flakes and dark soy sauce.
If using bell peppers, add them now and sauté for another 2-3 minutes.
Add the cornstarch slurry to the sauce, stirring continuously until it thickens.
Add the fried tofu cubes to the sauce and gently toss to coat them evenly.
Garnish with chopped spring onions.