Whisk together the flour, cornflour, baking powder, salt, pepper, and garlic granules. Pour in the fizzy water and whisk until there are no lumps.
Slice off the muddy ends from the mushrooms and break into around 10 evenly sized clumps.
Add enough oil to cover the mushrooms to a pan safe for deep frying and heat to around 175℃/350℉. (Alternatively, if you don't want to use too much oil, just add enough to half cover the mushrooms, flip them and fry for a little longer.)
Fry the mushrooms in batches until golden brown ensuring the oil remains at175℃/350℉. Flip a couple of times so they are evenly cooked. Remove carefully with tongs and drain on a wire rack whilst you fry the remaining batches.
Now, make the sauce. Heat the oil in a medium frying pan over a medium high heat. Add the garlic and fry for 30 seconds. Reduce the heat to low and add the ketchup, sugar, gochujang, and rice vinegar. Stir until bubbling. Stir in the sesame seeds before adding the mushrooms and tossing until completely coated in the sauce.
Serve the mushrooms hot garnished with the sliced spring onion.
