Start by preparing your yuba katsu. Slice your piece of yuba so that it fits your desired sandwich size.
Next prepare three plates. On one plate, mix together crushed cornflakes, salt, pepper, garlic powder and paprika. On another, just add the milk and on the final plate add your cornstarch.
Start by coating the yuba in cornstarch, then dip it in the milk to coat and finally into your cornflake mixture. Press in the coating as much as possible, then transfer to a baking tray or into your airfryer.
If using an airfryer, give the yuba a quick spritz with a spray oil then cook for 12-15 minutes at 375F, or until golden brown and crispy. If baking in the oven, bake for 10 minutes on each side, flipping once.
To assemble the sandwich, remove crusts from your slices of bread. Butter each side and add a layer of mustard to one side. Add your katsu on top of the mustard and drizzle with katsu sauce. On the other slice of bread, add your shredded cabbage. Close up the sandwich then press under a heavy plate for 5 minutes.
Slice in half and enjoy!