The karaage coating, traditionally used with chicken, is exceptionally crispy, moist and saporous.
Great patience is required for the tofu to get spongious: see step 1 for details!
To get the perfectly spongious texture you will need to freeze and unfreeze the tofu twice, so you will have to start 2-3 days before cooking. To make sure no bacteria may appear the tofu needs to always be kept below 5°C/40°F, so both unfreezing phases need to be made in the fridge.
Press the tofu block to get rid of any excess of water, then cut into cubes or chunks, lay in a sealable container and freeze (overnight for instance), then unfreeze in the fridge (all day for instance). Repeat again. After the second unfreezing phase you are ready to start with the marinade.
Blend the ginger, garlic, soy sauce, sake, mirin, nutritional yeast and black pepper.
Soak the tofu chunks (using a clean tea towel for instance), so they absorb the marinade better, and marinate for at least one hour in the fridge.
Heat the frying oil. Toss the tofu bites into tapioca starch and fry for a few minutes until you get a golden coating. Soak the oil excess using a towel and serve with rice, spring onions and mayonnaise.