Press your tofu, either with a tofu press, or by placing the tofu on a plate with another plate on top of it and then placing something heavy on top like a heavy pot. Leave it to press for 30 minutes.
Cut your tofu into cubes and add the cubed tofu to a bowl or container with a lid.
Add the cornstarch, nutritional yeast, garlic powder, onion powder, ground ginger, salt, pepper and chili flakes to the bowl.
Put on the lid and rotate the bowl a few times so that all the tofu cubes are covered in the spices and it's all well mixed.
Heat up a frying pan with the sesame oil and when it's hot, add your tofu cubes. Let them fry for a couple of minutes before gently turning them over and frying them on the other side.
Add the chopped green onions and toss with the fried tofu.
Add the soy sauce, water, maple syrup, rice vinegar and cornstarch to a measuring jug. Whisk until well mixed.
Pour this over your tofu and gently toss the tofu in the sauce until the sauce is mostly evaporated and the tofu is browned, crispy and sticky.
Add in the black sesame seeds and toss them with the tofu.