Drain the excess marinade from the tofu into a small bowl or mug and set aside for later. Pat the tofu dry with clean kitchen paper, squeezing out any excess liquid, then slice into strips about 1cm thick, then slice each strip into triangles or cubes. Toss these in the cornflour, then heat sunflower oil in a griddle or frying pan (enough to cover most of the bottom of the pan), then fry the tofu until golden and crispy on both sides. Remove to a piece of kitchen paper and set aside.
Slice the baby courgettes in half, and griddle or fry on both sides until golden and crispy then remove and add to the tofu. Finally, trim and slice the spring onions diagonally and fry these for a minute or two until just starting to char at the edges. Remove and add to the tofu and courgettes.
Wipe out the pan and add a little sunflower oil. Peel and finely chop the shallot and add to the pan, fry over a medium heat for 2-3 minutes until starting to soften. Add the garlic and ginger, then de-seed and slice the chilli and add to the pan. Cook over a medium heat for a further 2-3 minutes.
Tip the bowl of leftover tofu marinade into the pan, followed by the soy sauce and water. Bring to the boil, then when it has reduced slightly (1-2 minutes), add the tofu and courgettes and stir to coat. Remove from the heat, sprinkle over the sesame seeds and coriander and stir, then serve immediately with fluffy rice.