To begin, we'll work with the tofu. Remove and drain the tofu and be sure to press for about 30 minutes to ensure it is no longer dripping.
With your hands, break off bite size chunks from the tofu and add to a clean bowl. The pieces should be irregular in shape but make sure they are roughly the same size.
To the bowl of tofu, sprinkle in the cornstarch and toss to combine.
At medium heat, add the oil to a shallow pan, then add the tofu and fry. This may take some time, 15-20, minutes but we're looking for the edges of the tofu to become slightly brown and have a crispy exterior but with a little bounce to each piece.
While the tofu is frying, add all the ingredients for the sauce into a separate bowl and stir until combined. Set aside.
Once the tofu is done frying, remove it from the hot pan. Add the onions and peppers to the still hot pan. Fry the vegetables for about 4-5 minutes on high heat. They should be cooked through but still have a little crunch to them.
Next, reduce the heat, and add the tofu and the sauce to the pan with vegetables in it. Keep a little heat under the pan and stir to coat all the vegetables and tofu with the sauce mixture. Remove from heat.
Finally, garnish with the spring onions and serve hot!