Baked Mung Bean Custard (Khanom Mo Kaeng)

Ingredients

Equipment Needed

• •Steamer basket with cheesecloth
• •9-inch square or round baking pan
• •Fine-mesh sieve for mashing beans
• •Small frying pan for shallots

Instructions

1. 1

   Steam the mung beans

   Drain the soaked mung beans and spread them in a steamer basket lined with cheesecloth. Steam over boiling water for 20 to 25 minutes until the beans are completely soft and collapse when you press them between your fingers. No resistance. If there's any graininess left, keep steaming. Undercooked beans will ruin the custard's texture. While still hot, mash the beans with a fork or push through a sieve until you have a smooth, thick paste. No lumps. The paste should be the consistency of mashed potato.

   Steaming mung beans gives a drier, cleaner result than boiling. Boiled beans absorb excess water and dilute the custard. The same principle applies to sticky rice: steam, never boil. Moisture control matters.
2. 2

   Infuse coconut cream with pandan

   Pour the coconut cream into a saucepan with the knotted pandan leaves. Heat gently over low heat, stirring occasionally, for about 5 minutes. Don't let it boil. You're extracting the pandan's grassy, vanilla-like aroma into the fat of the coconut cream. The cream should smell intensely floral and green. Remove the pandan leaves and squeeze them over the pot to get every last drop of flavor out. Set aside.

   Fresh-pressed coconut cream has a richness that canned cannot match. The fat content is higher, the flavor is cleaner, and the custard sets with a silkier texture. If you use canned, use a brand with no additives or stabilizers. Shake nothing. Open the can and scoop only the thick cream from the top.
3. 3

   Melt the palm sugar

   Add the chopped palm sugar to the warm pandan coconut cream. Stir over low heat until completely dissolved. This takes patience. Palm sugar is dense and doesn't melt like white sugar. Stir steadily. You'll smell butterscotch and dark caramel as the sugar melts. When the mixture is smooth and homogeneous with no visible crystals, add the salt and remove from heat. Let it cool to warm, not hot. If you pour hot sugar-cream into eggs, you'll get sweet scrambled eggs. Nobody wants that.

   Ajarn always said palm sugar is non-negotiable in Thai sweets. Nam tan pip caramelizes differently from granulated sugar. The complex sugars produce deeper browning, richer aroma, and that signature butterscotch note that defines khanom mo kaeng. Substituting white sugar gives you a custard. It doesn't give you this custard.
4. 4

   Fry the shallots

   While the sugar mixture cools, heat the vegetable oil in a small pan over medium heat. Add the sliced shallots and fry slowly, stirring constantly. This is not a fast process. You want them to turn golden evenly, then deep amber. Pull them out just before you think they're done. They keep cooking in residual heat. Drain on paper. They should be crispy, sweet, and deeply caramelized once cool. Reserve the shallot oil separately. You'll use it too.

   Fried shallots burn in seconds. The window between golden and burnt is tiny. Better to pull them early and let carryover heat finish the job. Bitter shallots on top of a perfect custard is a tragedy.
5. 5

   Build the custard

   Preheat your oven to 170°C (340°F). In a large bowl, beat the duck egg yolks and whole eggs together until smooth. Don't whip air in. You want a smooth, homogeneous egg mixture, not a frothy one. Air bubbles create a spongy texture instead of the dense, silky custard you're after. Stir the warm palm sugar coconut cream into the eggs gradually, a ladle at a time, stirring constantly. Then fold in the mashed mung bean paste. Mix until everything is completely integrated. The batter should be thick, golden-brown, and smell like pandan and caramel.

6. 6

   Prepare the pan

   If using banana leaf, wilt the pieces briefly over a flame or in hot water until they're pliable, then use them to line a 9-inch square or round baking pan, letting the edges come up the sides. Brush the banana leaf with a little shallot oil. If not using banana leaf, brush the pan with shallot oil. Banana leaf isn't decoration. It's a cooking vessel. It prevents sticking, imparts a faint grassy sweetness, and makes the custard easier to cut and serve at room temperature. That's function, not aesthetics.

   At temple fairs in Phetchaburi, khanom mo kaeng is always baked in banana leaf-lined brass trays. The banana leaf insulates the edges and gives the custard a barely perceptible herbal note. If you can get banana leaf, use it.
7. 7

   Bake the custard

   Pour the custard batter into the prepared pan. It should come about 3/4 up the sides. Bake at 170°C for 40 to 50 minutes. Here's how you know it's done: the top should be deeply caramelized, a crackly dark golden-brown surface that's almost burnt-looking but isn't. The center should still have a slight jiggle when you shake the pan. A toothpick inserted near the center comes out mostly clean with just a trace of moisture. The custard sets as it cools. Overbaking gives you something dry and grainy. Pull it when the top is dark and the center barely trembles.

8. 8

   Cool and finish

   Let the custard cool in the pan for at least 30 minutes. It firms as it cools. Scatter the crispy fried shallots generously across the top. Drizzle a small amount of the reserved shallot oil over the surface. Cut into rectangles or diamond shapes. Khanom mo kaeng is served at room temperature, never hot. The flavors are best when the custard has set completely: dense, silky, with the palm sugar's butterscotch depth, the richness of duck egg and coconut, and that hit of crispy shallot on every bite. Sweet and savory. That's the Thai way.

Chef Tips

• •Duck eggs (khai pet) are essential here. They have a higher fat content and larger yolks than chicken eggs, which gives the custard its signature richness and deep golden color. Chicken eggs make a paler, lighter custard. It's edible but it's not khanom mo kaeng. Thai baking has always used duck eggs for this reason.
• •Palm sugar quality varies wildly. The best nam tan pip comes from Phetchaburi province, made from sugar palm (tan) sap collected fresh and cooked down to a dense, moist disc. Good palm sugar is soft enough to cut with a knife and smells like butterscotch. If your palm sugar is rock-hard, bone-dry, or tastes like plain sugar with brown food coloring, find a better source. An Asian market with Thai imports is your best bet.
• •The Portuguese influence on Thai sweets is real and traceable to one person: Maria Guyomar de Pinha (Thao Thong Kip Ma), who brought egg-based confectionery techniques to King Narai's court in the 17th century. The Portuguese used cane sugar, butter, and wheat flour. Thai cooks took those techniques and replaced every ingredient with their own: palm sugar for cane sugar, coconut cream for butter, rice flour for wheat. The technique was absorbed. The principles stayed Thai. Foi thong, thong yip, thong yod, and khanom mo kaeng are all descendants of that cultural transformation.
• •Khanom mo kaeng is a make-ahead dessert. It actually improves after resting overnight in the refrigerator. The flavors deepen, the texture firms, and the palm sugar's complexity becomes more pronounced. Bring it to room temperature before serving. This makes it perfect for temple fairs and family gatherings, which is exactly where it lives.

Advance Preparation

• •Mung beans must be soaked overnight, at least 8 hours. Don't skip this. Unsoaked beans take forever to steam and never get as smooth.
• •The mung bean paste can be steamed and mashed a day ahead. Refrigerate in an airtight container.
• •Fried shallots can be made up to 3 days ahead and stored in an airtight container at room temperature. They lose crispness in humidity, so fry them fresh if you're in a tropical kitchen.
• •The finished custard keeps well for 3 to 4 days refrigerated. Bring to room temperature before serving. Add the fried shallots just before serving to keep them crispy.

Frequently Asked Questions

Nutrition Information

1 serving (about 160g)