Cooking in
British Columbia
Thai
Tub Tim Grob (Red Ruby Coconut Milk Dessert)
Water chestnuts coated in red-dyed tapioca flour, briefly cooked to a chewy, slightly crunchy exterior, served in sweetened coconut milk with crushed ice — the dessert that most vividly expresses the Thai kitchen's relationship with texture as flavour. Tub tim means ruby (from the deep red colour); grob means crunchy-crisp. The preparation's excellence is in the contrast between the ice's cold, the coconut milk's sweetness, and the coated water chestnut's unique chewy-crunchy texture — the tapioca coating translucent and yielding on the outside, the water chestnut crisp within.
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Cook
I
The Market List
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300 g
Fresh water chestnuts
peeled and diced into 1 cm cubes
Origin · ChinaChoose your town to see who stocks it →
1 tsp
Red food colouring
liquid; sufficient for a deep red
Not yet stocked in British Columbia
100 g
Tapioca flour
not tapioca pearls; for coating
Not yet stocked in British Columbia
For the sweet coconut milk
500 ml
Coconut milk
full-fat; chilled after sweetening
Origin · Sri Lankan coconut (Coconut Research Institute of Sri Lanka), Sri LankaChoose your town to see who stocks it →
60 g
1 pinch
Salt
Your own market
To serve
250 g
Crushed ice
prepared just before service
Your own market
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II
The Method
1
Place the diced water chestnuts in a bowl, add the red food colouring, and toss to coat evenly so the colour penetrates the cut surfaces rather than sitting as a thin film that will wash off in the boiling water. Set aside for 10 minutes. The pieces are ready when the colour is absorbed and the surface is uniformly deep red.
2
Add the tapioca flour to the bowl and toss the water chestnuts until every surface is coated, so each piece carries an even layer that will cook into a smooth, unbroken shell rather than a patchy one with thin spots. Shake off any loose excess. The coating should be dry and opaque white — no bare patches visible.
3
Bring a generous volume of water to a full boil and drop in the coated water chestnuts, stirring immediately so the pieces do not cling together and fuse before the coating sets. This is where the dish lives or dies: at 60 seconds the coating remains powdery and under-gelatinised; beyond 2 minutes it begins to dissolve and lose structural integrity. Cook for exactly 90 seconds, at which point the coating turns from opaque white to translucent and acquires its characteristic chewy resilience.
4
Lift the pieces immediately with a slotted spoon and rinse under cold running water so that the heat inside the coating is arrested at once and the outer surface does not continue softening on its way to the bowl. The coating should feel slightly yielding under gentle pressure, with the firm water chestnut detectable within.
5
Combine the coconut milk, palm sugar, and salt in a saucepan over low heat, stirring until the sugar is fully dissolved; keeping the heat low prevents the coconut milk from splitting and turning grainy, which would break the clean, silky sweetness you are after. Remove from the heat, cool to room temperature, then chill completely. The liquid should taste sweet with a clean saline edge.
From the canon — Palm sugar — made from the sap of the palmyra palm (Borassus flabellifer) or coconut palm — is the primary sweetener of the Thai kitchen and one of the most … Palm Sugar (Nam Tan Pip): Selection and Use →
6
At service, place a mound of crushed ice in each bowl and pour the cold sweetened coconut milk over the ice so the liquid chills instantly on contact rather than melting the ice into a diluted pool. Float the coated water chestnut pieces on top. The coconut milk should be visibly cold, with the ice intact and the red jewels resting on the surface.
III
Quality Hierarchy
01
Reserve — Fresh water chestnuts, peeled to order, from a Chinese or Asian grocer; coconut milk pressed from a whole fresh coconut; palm sugar from a solid block, shaved fine.
02
Estate — Fresh water chestnuts as above; good-quality canned or carton coconut milk with no stabilisers; palm sugar in soft paste form.
03
Market — Canned water chestnuts, drained and dried — expect approximately 60 per cent of the textural character of fresh; standard canned coconut milk; palm sugar or soft light brown sugar.
04
House — Canned water chestnuts with canned coconut milk and granulated white sugar — the dessert remains coherent but the crunch-and-chew contrast, its essential point, is diminished.
IV
Sensory Tests
◇Sight. The tapioca coating turns from opaque white to translucent during the 90-second boil — full translucency signals the gelatinisation is complete.
◇Touch. A coated piece pressed gently between thumb and forefinger yields slightly at the exterior while the water chestnut within resists — chewy outside, crisp within.
◇Sight. The finished bowl shows ice still intact and unmelted, coconut milk cold and barely fluid around it, red pieces floating — service must be immediate.
◇Smell. The sweetened coconut milk, fully chilled, carries a clean, faintly grassy coconut fragrance with no sourness — sourness indicates the milk has been held warm too long.
◇Where it lives or dies. The dish stands or falls on the 90-second boil and the immediate cold-water rinse: too short and the tapioca coating remains powdery; too long and it dissolves — only at 90 seconds does it set translucent, chewy, and structurally sound.
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VI
What to Pour
No alcoholic pairing is indicated. Jasmine tea, served hot alongside, provides an aromatic counterpoint to the cold, sweet bowl — the heat of the tea in contrast to the iced dessert mirrors the preparation's own logic of contrast.
The whole pairingPillar VII
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The working kitchen
Sourced through Provenance