Drain the tofu, pat dry with a paper towel, and cut into small cubes
Place the cornflour in a large bowl, take a cube of tofu, coat it in the flour and place on a plate
Repeat for the rest of the tofu, adding extra cornflour if necessary
Heat up the oil in a frying pan until hot
Once the oil is hot, keep it on a medium heat and add the cornflour-coated tofu
Fry for a few minutes on each side, turning over halfway through (it's easiest to do this using chopsticks). Cook it until it’s crispy and lightly browned, but be careful not to overcook, otherwise it’ll become tough
Transfer the cooked tofu onto a plate lined with kitchen paper (to drain away the excess oil)
For the sauce:
Heat up the oil in a frying pan - you can use the same frying pan you used to fry the tofu
Add the ginger and garlic once hot and fry for a couple of minutes until fragrant
Add all the other ingredients
Place the cornflour in a small bowl and dissolve in a tiny splash of water - make sure it has completely dissolved
Keeping the pan on a low heat, carefully add the cornflour mixture, stirring regularly to avoid clumping
Keep heating until the sauce is thickened - add an extra splash of water if it’s too thick
Add the cooked tofu and mix well
Sprinkle over thinly sliced spring onion and sesame seeds, if desired
Best enjoyed immediately, but leftovers can be kept covered in the fridge for up to a few days, and can be reheated in a frying pan
Notes
Be very careful with cornflour as it can easily turn clumpy. Dissolve it first in a tiny splash of water in a small bowl, until you get a small amount of white liquid (make sure it's not too thick). Make sure it has dissolved completely. Add the cornflour mixture carefully a tiny bit at a time, stirring well to ensure it doesn't clump. If the texture of the sauce looks too thick after you've added the cornflour, add extra water.