Put 1 tablespoon of the cornflour in a bowl and then toss the tofu in it until all pieces are well coated.
280 g extra-firm tofu, 2 tablespoon cornflour
Get a wok on the hob with 1 tablespoon of oil and get it to a medium-high heat. Add the tofu and cook until nicely browned and it has a bit of a crisp outside, then take the tofu out and set to one side for later.
2 tablespoon oil
Optionally, add the remaining 1 tablespoon of oil (or oil spray), and bring back up to a medium heat, then pop in the peppers and chilli (if using) in and fry for 2-3 minutes.
2 tablespoon oil, 2 red peppers, 1 red chilli
Add the spring onions and stir fry for one more minute.
8 spring onions
Now get the broccoli, pineapple, ketchup, vinegar, sugar and stock in there - give it a good mix and bring it up to a boil.
200 g broccoli, 200 g pineapple, 4 tablespoon tomato ketchup, 2 tablespoon apple cider vinegar, 1 tablespoon brown sugar, 250 ml vegetable stock
While the sauce is coming up to a simmer, mix the remaining 1 tablespoon of cornflour with a splash of water until you have a thick, but still slightly runny paste - stir it into the sweet and sour tofu sauce.
2 tablespoon cornflour
Add the tofu back in and cook for 2-3 minutes, until hot. Season with salt, to taste.
Salt