Remove the tofu from its packaging, pat it dry with kitchen paper and squeeze out any excess moisture, then slice it into three large, flat slices.
Pat each slice dry with kitchen paper, then set them aside to dry out further.
For the sauce:
Heat the oil in a deep frying pan or casserole. Finely chop the onion, garlic and ginger and add them to the pan. Cook gently to soften.
Add the turmeric and curry powder, and cook for a further minute at a gentle heat, then stir through the plain flour.
Add the vegetable stock a little at a time, stirring well so no lumps of flour remain.
Bring the sauce to a gentle simmer, then add the coconut milk, sugar and soy sauce. Let the sauce bubble gently for 10-15 minutes then turn off the heat and set aside to cool.
For the crispy tofu:
Meanwhile, prepare the batter for the tofu by mixing the plain flour, dairy-free milk and soy sauce in a small bowl. Whisk well until no lumps remain.
Pour the batter into a plate or shallow bowl, and tip the panko breadcrumbs into another plate or bowl.
Take one slice of tofu, and dip it in the batter on both sides until it is fully coated. Lift it out and shake gently so the covering of batter is fairly thin.
Place it straight into the plate of panko breadcrumbs, then cover it, pushing down gently so they stick all over it.
Set aside and repeat for the remaining tofu slices.
Pour oil about 2cm deep into a deep frying pan, and heat it for shallow frying. If you have a kitchen thermometer, it needs to get to 180°C / 350°F. If you don't have a thermometer, combine some leftover batter and breadcrumbs and drop a small spoonful into the oil. If it sizzles and turns brown within about 20-30 seconds, the oil is ready.
When the oil is hot enough, carefully add one or two slices of tofu. Don't crowd the pan - it is best to cook one or two at a time, rather than all three. Let them cook for a minute or two then turn over to the other side.
Keep cooking and turn occasionally until they are golden and very crispy - ideally about 2-3 minutes on each side. If they are cooking too quickly, turn the heat down a little.
When they are cooked, remove them to a piece of kitchen paper and set aside. Remove the oil from the heat, and let it cool completely.
To finish the sauce:
Pour the sauce into a blender or food processor, or use a stick blender to blitz it to a very smooth purée. If you can't get it as smooth as you like, you can pass it through a fine sieve, (though use a metal sieve if you can, or it may be stained by the turmeric).
Return the sauce to the pan to heat through. Slice the tofu into thick slices, and serve with rice, with plenty of katsu sauce. Sprinkle with fresh coriander, finely sliced spring onion, sesame seeds and a generous squeeze of lime.