Khanom Mo Kaeng (ขนมหม้อแกง)

The Custard With The Burnt Face

ขนมหม้อแกง is Phetchaburi's royal dessert — the coconut custard that Thailand baked before ovens existed. Kapook's introduction to the recipe is the craving everyone recognises: nobody's going to Phetchaburi today, so we make it ourselves. The dish's signature is visible in every photo of it: the หน้าไหม้, the burnt-gold face on top, caramelised from the fried shallots scattered over the surface before baking.

The shallots do double duty, and the sources agree on both halves. First, the shallots are fried in oil until golden — then given five seconds on high heat, Wongnai's detail, so they don't come out greasy. Second, the frying oil itself goes into the batter: two tablespoons of shallot oil stirred through the custard, so the fried-onion perfume runs through every bite, not just the top.

Pim's recipe page records how it was made before the oven: a sheet of thick zinc laid over the charcoal brazier — the bottom heat — the custard tray centred on it, a second zinc sheet over the tray, and live coals piled on top — the top heat. The modern oven just does the same job at 170°C. The recipe itself is the same everywhere: eggs and pandan squeezed, palm sugar kneaded in, coconut cream and the filling, the shallot oil, the bake. Only the filling changes.

The Recipe (the mung-bean classic, from Wongnai)

The taro version (Kapook, Pim): swap the mung bean for 300 g steamed taro, mashed into the mixture — same eggs, cream, sugar, pandan and shallot oil, baked at 170°C about 20 minutes in cups.

The Method

1. The shallots. Fried in the oil over medium until golden, then five seconds on high; drained on a sieve. Two tablespoons of the frying oil kept for the batter.
2. The squeeze. Eggs and pandan squeezed together until fluffy; coconut sugar kneaded in until it fully dissolves.
3. The batter. Coconut cream and the ground mung bean in; the two tablespoons of shallot oil stirred through.
4. The bake. Into the dish, fried shallots scattered over the top, baked until set and the face burns gold. 170°C, ~40 minutes in a tray, 20 in cups.
5. The cut. Cooled, cut into squares — the burnt top is the prize.

Where Thai Sources Disagree

How Western Versions Get It Wrong

• Calling it flan or crème caramel. No water bath, no caramel syrup — the sweetness is palm sugar in the custard, and the top is fried shallots, not caramel.
• No shallots. The fried shallots and the shallot oil in the batter are the dish's signature perfume. A plain coconut custard is a different dessert.
• White sugar instead of palm. Coconut sugar is the flavour — toffee, smoke, depth. White sugar makes it generically sweet.
• Covering the bake to keep it pale. The golden-burnt face is the dish's mark of pride. A pale top is a failed mo kaeng.
• Skipping the squeeze. The eggs must be squeezed with pandan until fluffy — it's the texture step that makes the custard light instead of dense.

UK Ingredient Notes

• Mung beans: dried or tinned at South Asian grocers — steam and grind.
• Coconut sugar: Thai grocers or the sugar aisle of big supermarkets.
• Coconut cream: thick tinned cream works; pandan leaves frozen at Thai grocers.
• Duck eggs: farmers' markets; all-chicken works with a lighter set.
• Taro for the taro version: frozen at Chinese grocers.

Sources

This recipe is translated from the following Thai-language sources. Where they disagree, we've said so.