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1
Combine the kanten powder with 500 ml cold water in a small heavy saucepan. Let the powder hydrate for two minutes, then place over medium heat, stirring continuously until the kanten has fully dissolved and the liquid is clear with no visible granules — the surface should be completely transparent when a spoon is lifted.
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2
Add the sugar (350–400 g according to the crystallisation character desired) and stir until fully dissolved. Bring the mixture to a gentle boil and maintain for two minutes, stirring; the syrup should coat the back of a spoon and look uniformly glossy with no sugar crystals visible at the pan's edge.
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3
Remove from heat and allow the mixture to cool slightly — to below 80 °C if using butterfly pea flower tea or other heat-sensitive natural pigments. Stir in the chosen flavouring and colouring at this point; adding colour to a still-boiling mixture bleaches pigments and cannot be reversed. The liquid should be evenly tinted, translucent, and fluid.
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4
This is where the dish lives or dies: pour the mixture immediately into a shallow tray to a depth of exactly 1.5–2 cm. Work quickly — kanten sets faster than gelatin, and any hesitation will produce an uneven surface that traps bubbles and creates a weak, non-uniform crystal layer. Tap the tray once on the bench to level; do not stir or disturb the surface thereafter. The poured liquid should be still, level, and luminous.
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5
Allow the tray to set at room temperature until firm — approximately 30 minutes. The surface should feel dry to a very light touch and show no movement when the tray is gently tilted. It will be cooler than the ambient air and faintly resilient underfoot of a finger.
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6
Turn the set kanten slab onto a clean cutting board. Using a sharp knife, cut into geometric pieces — diamonds, rectangles, or irregular gem-shapes — of one- to two-bite size. Arrange the cut pieces on wire racks, spaced so no two pieces touch, to maximise air circulation on all faces.
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7
Leave the pieces uncovered at room temperature for 3–5 days, turning once daily. Do not refrigerate and do not dry in a warm oven — uniform heat produces even dehydration without surface crystal nucleation. After 3–5 days, the exterior should be visibly granular and shimmering, with a faint crunching sound when a fingernail is lightly drawn across the surface. Do not cut or handle the pieces before this point; reopening the surface dissolves the crystal layer.
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8
Test a single piece: the exterior should yield a clean, glassy crack when bitten, followed immediately by a soft, yielding gel interior. The interior colour should be translucent, the exterior opaque with sugar crystals. If the surface remains tacky, continue drying; if the interior has crystallised throughout, the sugar ratio was too high.