Tofu of sesame seeds, thickened with kudzu starch. Decide on the characteristics of your gomadofu by adjusting the quantity and quality of the three main ingredients - kudzu starch, sesame seeds and liquid medium.
In a mixing bowl, dissolve the kudzu starch with a little dashi to form a slurry. Use the back of a spoon to break up any lumps.
In a blender, blend sesame seeds or tahini and kudzu slurry with the remaining dashi. Strain the mixture through a cheesecloth or nut milk bag into a heavy-bottom saucepan.
To the mixture in the saucepan, add salt and sake, if using. Cook the mixture over medium heat, stirring all the time. After 2 to 3 minutes you will feel the mixture beginning to thicken. At the point reduce the heat to low and cook for another 10-15 minutes, stirring all the time. By the end of the cooking, the mixture should develop a strong elasticity.
Wet a square or rectangular mold with water (this is to keep it from sticking). Pour the mixture into the mold and working quickly as it sets fast, smooth the surface with a spatula. Put 2 to 3 tablespoons of cold water over the surface of the mixture to prevent it from drying out.
Place the mold in the refrigerator to set for at least 3 hours or for as long as over night.
When solidified, unmold and slice gomadofu into squares. Keep in water until ready to serve.
In a small saucepan, combine the dashi, tamari, and mirin, and bring the mixture to a boil. Remove from heat, and let the sauce cool to room temperature. Store sauce in the refrigerator until serving.
Just before serving, prepare wasabi paste by mixing wasabi powder with warm water to form a paste. Set aside for 5 minutes to allow the full flavour to develop.
To serve, place a square of gomadofu in a small bowl. Spoon a little sauce over the gomadofu and garnish with a dab of wasabi paste.
To prepare vegan dashi, soak 1 piece (16 square-inches) kombu and 1 dried shiitake mushroom in 4 cups water in a saucepan for 2 hours or longer. Bring to a low simmer, below boiling, then turn off the heat and steep until the dashi cools to room temperature. Remove the kombu and shiitake mushroom. This is the first (ichiban) dashi. They can be reused one or time to make second (niban) dashi, but the dashi strength will be weaker.
Blend 80 g (1/2 cup) sesame seeds or tahini with 120 g (1/2 cup) dashi and 1/3 cup prepared Irish moss paste. Pour into a shallow pan and allow to set overnight before slicing.