To soften the peanuts
Mix the peanuts and water in a bowl, cover and leave to soften in the fridge for approx. 24 hrs.
Puree the peanuts with the peanut water, pour the mixture through a sieve lined with a cheesecloth, squeeze out all the liquid. In a pan, combine the reserved liquid with the potato starch. Bring to the boil while stirring, cook for approx. 2 mins., then pour into the dish and smooth down. Place cling film directly on top of the mixture, leave to cool. Cover and chill for approx. 6 hrs. Cut the peanut tofu into cubes or slices.
Place the soy sauce, mirin and sugar in a pan, bring to the boil while stirring. Leave the sauce to cool, serve with the peanut tofu.