Remove tofu from package after draining liquid out, then wrap the tofu in some paper towel. Place it on a plate and lay another plate on top to press out the excess water. Leave for 30 minutes at least.
Roast the sesame seeds over medium heat in a dry frying pan until they brown and start popping. Take care not to burn them!
Grind the sesame seeds in a suribachi (a mortar and pestle or food processor can also work) until they become powdery. Add the miso, mirin and sugar, and blend well.
Squeeze the tofu gently until it’s as firm as your earlobe, then add to the ingredients in the suribachi. Add a pinch of salt if the mix isn’t salty enough yet, and continue grinding until creamy.