Bring the double strength vegetable stock to a rolling boil and stir in the yeast extract or soy sauce
Add the soy protein chunks, remove from heat, cover, and leave to stand for 10 minutes until fully rehydrated
Drain the chunks and squeeze out all excess liquid until as dry as possible
Heat a generous splash of oil in a wide pan over medium-high heat
Add the rehydrated chunks and fry until deeply golden and crisp all over, allowing them to sit before stirring
Push the chunks to the side of the pan and season well
Add a little more oil if needed and fry the spring onions, chilli, ginger and garlic for 1-2 minutes until fragrant
Add the black pepper and toast briefly
Stir in the ketchup, soy sauce, sriracha, rice wine vinegar and sugar, letting it bubble for a minute
Toss everything together so the chunks are well coated and season well
Pour in the cornflour slurry and cook for 1-2 minutes until glossy and sticky
Loosen with water if desired and adjust seasoning
Serve hot on a bed of rice
