A steamed egg custard of duck eggs, thick coconut cream, palm sugar, and pandan leaf — either steamed free-standing in a bowl, steamed inside a hollowed pumpkin (sangkaya fak thong — the most elaborate version), or used as a filling. Sangkaya is a preparation that entered the Thai dessert tradition via Portuguese culinary influence in the 17th century — the custard-making technique (egg, fat, sugar, set by gentle heat) is recognisably related to the Portuguese ovos moles and the flan tradition. The Thai adaptation substitutes duck eggs (with their richer, more orange yolks) for chicken eggs, replaces dairy cream with coconut cream, and adds pandan for its aromatic.
**Ingredient precision:** - Duck eggs: higher fat content in the yolk (approximately 14% vs 10% for chicken eggs), producing a richer, more intensely golden custard. Substitute with chicken eggs if unavailable. - Thick coconut cream (hua kati): first pressing only. The fat content of the cream determines the custard's richness. Second pressing produces a lighter, less satisfying custard. - Palm sugar: dissolved and slightly cooked before combining — this step caramelises the palm sugar slightly, deepening its flavour beyond the raw dissolved state. - Pandan leaf: bruised and tied into a knot, added to the custard mixture and steeped for 15 minutes before straining out. The pandan's 2-acetyl-1-pyrroline and other aromatic compounds infuse into the coconut cream during this steeping. **The custard ratio:** Duck eggs (4–5) : thick coconut cream (300ml) : palm sugar (150g dissolved). The ratio is approximately 1 egg per 60ml coconut cream — less egg-rich than a French custard (which uses more yolk per liquid volume) but producing a softer, more trembling set from the lower protein concentration. **Steaming the custard:** 1. Combine beaten eggs, coconut cream, and palm sugar. Strain through a fine sieve. 2. Pour into a heatproof bowl or the hollowed pumpkin. 3. Steam over barely simmering water (not boiling — a vigorous boil creates steam turbulence that produces bubbles in the custard surface) for 30–35 minutes for a 300ml custard. 4. The custard is done when the edge is fully set and the centre retains a slight tremor when the vessel is gently moved. **The pumpkin preparation (sangkaya fak thong):** - Select a small kabocha pumpkin (the Thai fak thong — dark green, dense flesh). - Cut off the top as a lid. Scoop out seeds and fibres. - Fill the cavity with the custard mixture. - Replace the lid. Place in a steaming basket. Steam for 45–55 minutes until the pumpkin flesh is tender and the custard is set. - Cool completely. Slice into wedges at service — each slice shows the orange pumpkin flesh and the set custard within. Decisive moment: The steaming temperature — the water beneath the steamer must never reach a vigorous boil during custard steaming. Violent steam turbulence: the custard surface develops holes and a coarse texture (the same mechanism as a poorly made crème brûlée baked in an oven that is too hot). The target: a gentle, steady steam from barely simmering water. The custard sets smoothly through radiant heat, not turbulent heat. Sensory tests: **The tremor test:** Gently move the steaming vessel. A correctly set custard trembles at the centre — a single, unified movement of the still-slightly-liquid centre — while the outer 2cm are fully set. Under-cooked: the entire surface moves as liquid. Over-cooked: no tremor, the surface is rubbery and the whey has separated (visible as a ring of liquid around the custard's edge). **Sight — the surface:** Correctly steamed Thai custard has a smooth, slightly glossy surface of deep amber-gold from the duck egg yolks and palm sugar. Tiny bubbles on the surface indicate the steam was too vigorous.
David Thompson, *Thai Food* (2002); *Thai Street Food* (2010)