Put the tofu and katakuriko into a heat-resistant bowl and mix until smooth. There will be lumps remaining from the tofu if it is not mixed well enough.
If it is not getting smooth enough, you can heat it in the microwave for roughly 1 minute to help.
Heat in a 550 W microwave for 1 minute 30 seconds with no cover. If there are still white parts left, keep heating for 30 seconds more, checking each time.
Once the color of the mixture has completely changed, it's finished. Leave to cool for a little while to make it easier to handle.
Pour liquid over the top. (Use soy sauce for isobe mochi and water for kinako.) Form into the right shape with a spoon and wrap with nori seaweed or sprinkle with kinako.