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NE-RI YŌKAN — DISSOLVING THE KANTEN. Combine the kanten and water in a medium saucepan. Bring to a full boil over medium heat, then maintain a rolling boil for a full two minutes, stirring constantly. The liquid must be entirely clear with no visible undissolved particles; any graininess at this stage will produce a faulty set.
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ADDING PASTE AND SUGAR. Reduce the heat to low. Add the bean paste and stir to combine fully. Add the sugar in two or three stages, tasting after each addition, until the sweetness is present but not aggressive — the target range is 60–70 g per 250 g paste. Add the salt. Continue stirring over low heat until the mixture is perfectly smooth and the sugar is dissolved; a lifted spoon should show a mixture that falls in a slow, unbroken ribbon.
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COOLING BEFORE MOULDING — THE DECISIVE STEP. Remove from the heat and allow the mixture to cool, undisturbed, until it reads 60–65°C. Pouring at higher temperatures entrains bubbles that will set permanently into the surface. Do not stir during this cooling; kanten that is handled repeatedly through heating cycles loses gelling strength. The mixture should still be fully fluid at 60–65°C but visibly thicker at the edges of the pan — this is where the yōkan lives or dies: pour too soon and the surface is pitted; pour too late and the mixture has begun to set in the pan and will not level.
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MOULDING AND SETTING. Lightly wet a square mould or loaf tin. Pour the mixture to a depth of 1.5 cm. Tap the mould gently once on the bench to release any remaining bubbles. Leave at room temperature, undisturbed, until fully set and cold — the surface should be firm and matte, with no tacky centre when pressed lightly with one finger.
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SLICING. Unmould onto a clean board. Using a wire cheese cutter or a hot dry knife wiped between each cut, slice to 5 × 3 cm portions. The cut edge should be glassy and smooth, with no tearing or dragging; a knife that is damp or cold will drag the surface.
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MUSHI-YŌKAN (STEAMED VARIANT). Combine the bean paste, sifted flour or kuzu, sugar, and salt in a bowl. Mix until a smooth, uniform batter forms — slightly looser than the ne-ri mixture, with no dry pockets of starch. Pour into a wetted mould. Steam at 90°C for 30–35 minutes. The yōkan is done when the surface is just set and firm to a light touch at the centre, and a skewer inserted withdraws clean.
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TŌRŌYŌKAN — CLEAR LAYER FIRST. For the transparent variant: dissolve and boil the kanten in 300 ml water for two full minutes. Pour a thin clear layer (approximately 5 mm) into the wetted mould. Allow to firm until the surface holds the weight of a petal without sinking. Press dried chrysanthemum petals or sakura leaves flat against the surface. They must be dry; any moisture will cause them to float when the next layer is poured.
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TŌRŌYŌKAN — PALE PASTE LAYER. Dissolve the shiroan into the remaining hot kanten liquid over low heat. Cool to 60–65°C as above. Pour gently over the set clear layer and trapped flowers. The pale layer should cover the petals entirely. Leave to set fully at room temperature. The finished block, held to the light, should reveal the suspended botanicals as distinct, jewel-like forms within a translucent field.
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STORAGE. Store cut pieces in an airtight container with a silica packet. Yōkan absorbs ambient humidity; exposure causes the surface to become sticky. Consume within three to five days for optimal texture.