Sankaya — Thai coconut custard steamed in a pumpkin

i. Origin & history

Sankaya belongs to the family of Thai egg-based sweets that developed after contact with Portuguese traders and missionaries in the sixteenth and seventeenth centuries. The best-known figure in this story is Maria Guyomar de Pinha, a woman of Portuguese, Japanese and Bengali descent who worked in the royal kitchens of Ayutthaya under King Narai in the late seventeenth century. She is widely credited with introducing or popularising Portuguese-style egg-yolk sweets such as thong yip, thong yot and foi thong. Whether she had a direct hand in sankaya is less certain, but the custard clearly belongs to the same tradition of eggs and sugar meeting Thai coconut and palm sugar.

The name is related to the Malay seri kaya or kaya, the coconut and egg jam spread on toast across Malaysia, Singapore and Indonesia. Both are made from eggs, coconut and sugar, and both are flavoured with pandan; the Thai version is set firmly by steaming, while kaya is stirred into a spreadable jam.

Sankaya is versatile. Steamed in a pumpkin, it is a showpiece for special occasions and markets. Steamed in a dish, it is spooned over sweet sticky rice as khao niao sangkhaya. And a looser, stirred, bright-green pandan version, sangkhaya bai toey, is served as a dip for soft steamed or toasted bread (khanom pang sangkhaya), a hugely popular night-market and café snack.

The pumpkin version is particularly associated with central Thailand and is sold whole or by the wedge in markets. Kabocha pumpkin, called fak thong ('golden gourd') in Thai, has dense, sweet, dry flesh that holds its shape well when steamed, making it the perfect vessel.

ii. How to steam a custard without holes

Sankaya is an egg custard, set by the coagulation of egg proteins as they heat. Eggs begin to set at around 62–70 °C and become fully firm above 80 °C. If the custard heats too fast or too much, the proteins tighten, squeeze out water and form bubbles and holes, giving a spongy, weeping custard. The secret is gentle, steady steam at medium-low heat for a long time, with a cloth under the lid to stop condensation dripping in.

Thai cooks traditionally dissolve the palm sugar by kneading it with the eggs and pandan leaves by hand. This squeezes the fragrant oils out of the pandan, breaks up the hard palm sugar and blends everything without whisking in air. Whisking vigorously creates bubbles that end up as holes in the set custard, so stirring should be gentle and the mixture strained before steaming.

The pumpkin needs careful preparation. It is hollowed out through a lid cut in the top, and the seeds and stringy membranes scraped out so the custard sits against firm flesh. Choosing a small, dense pumpkin with thick walls ensures it cooks in about the same time as the custard. An overripe or watery pumpkin can collapse or release water into the custard.

The sankaya must cool completely before cutting — ideally several hours or overnight in the fridge. Warm, the custard is too soft and will separate from the pumpkin; cold, it sets firmly and slices cleanly.

iii. Ingredients

Makes 6 servings · scroll the side panel to adjust

• 1 small kabocha pumpkin, about 1–1.2 kg
• 5 large eggs (or duck eggs)
• 150 g palm sugar, chopped
• 200 ml thick coconut cream
• 4 pandan leaves, cut into short lengths
• ¼ tsp salt
• 1 tbsp rice flour or tapioca starch (optional, for a firmer set)

Kabocha (Japanese pumpkin) is the classic choice; buttercup squash is a good substitute. Avoid large, watery carving pumpkins. Duck eggs are traditional and give a richer, firmer custard. Palm sugar gives the caramel colour and deep flavour; light brown sugar works but tastes different. Use the thickest coconut cream you can find. A spoonful of rice flour helps the custard set firmly and prevents weeping.

iv. Method

1. Wash the pumpkin. Cut a lid around the stalk at an angle, so it sits back without falling in. Scrape out the seeds and membranes with a spoon until the inside is clean and smooth.
2. In a bowl, put the eggs, palm sugar, salt and pandan leaves. Knead and squeeze together with your hand for 3–5 minutes, until the sugar dissolves and the mixture turns faintly green and fragrant.
3. Add the coconut cream and rice flour and stir gently without whisking. Strain through a fine sieve into a jug, pressing the pandan leaves.
4. Set the pumpkin on a heatproof plate in a steamer. Pour in the custard to about 1 cm below the rim and set the lid alongside, not on top.
5. Wrap the steamer lid in a cloth. Steam over medium-low heat for 45–60 minutes, until the custard is set and a skewer inserted in the centre comes out clean, and the pumpkin flesh is tender.
6. Leave to cool to room temperature, then chill for at least 3 hours or overnight.
7. Cut into wedges with a sharp knife and serve chilled or at room temperature.

v. Tips & common mistakes

• Steam gently. High heat makes the custard bubble and form holes. Medium-low steam gives a smooth set.
• Do not whisk. Knead or stir; whisking adds air that becomes holes.
• Strain the custard. It removes stray egg white and pandan fibre for a silky texture.
• Choose a dense, small pumpkin. Thick, dry flesh cooks in time with the custard and holds its shape.
• Wrap the lid. Condensation dripping onto the custard leaves pits and watery patches.
• Chill before cutting. Warm sankaya separates from the pumpkin when sliced.

vi. Variations

Sangkhaya bai toey is a stirred, green pandan custard served as a dip with bread. Khao niao sangkhaya spoons steamed custard over sweet coconut sticky rice. The custard can be steamed in a dish or in individual ramekins, or in young coconuts. Some cooks add taro or banana to the custard.

For other Thai sweets with coconut and egg, see khanom chan, coconut rice cake and butterfly pea flower pudding. The Malaysian cousin seri muka layers pandan custard over sticky rice, and Portuguese egg sweets live on in the Brazilian quindim.

vii. Serving & storage

Sankaya is served in wedges, chilled or at room temperature, as a dessert or afternoon snack. The pumpkin skin is edible once steamed, though many people eat only the flesh and custard. It pairs well with Thai iced tea or jasmine tea.

Keep covered in the fridge for up to 2 days. The custard may weep a little liquid over time; blot it before serving. Sankaya does not freeze well, as the custard becomes watery and grainy on thawing.

ix. More from Thai

• Coconut Rice Cake — Thai coconut sticky rice
• Khanom Chan — nine-layer cake
• Khao Tom Mud — banana sticky rice parcels
• Tub Tim Krob — 'crisp rubies' in coconut milk
• Seri Muka — pandan custard rice cake
• Quindim — Brazilian egg yolk custard