Kue Lumpur — soft potato and coconut-milk 'mud' cakes

i. Origin & history

Kue lumpur belongs to the large group of Indonesian kue basah — soft, fresh cakes eaten as snacks, served at gatherings and sold at markets. It is particularly associated with Jakarta and the Betawi and Javanese kitchens, and is found across Indonesia and in Malaysia and Singapore, where it is called kuih lumpur.

Its ingredients point to the colonial-era meeting of Dutch and Indonesian cooking. Potatoes, butter, eggs and raisins came into Indonesian baking during the Dutch period, when European-style cakes and pastries were adapted with local ingredients such as coconut milk and pandan. Many classic Indonesian snacks share this mixed heritage, including lapis legit and kue cubit. The name, by contrast, is pure Indonesian: lumpur means mud, describing the wet, soft batter and the gently yielding cake.

Kue lumpur is a staple of arisan (social gatherings), selamatan (ritual feasts), weddings and Lebaran, and is commonly bought by the box from cake shops for office meetings and family visits. Its golden colour and raisin topping make it easy to recognise among the green and white cakes on a jajanan pasar tray.

A different snack, kue lumpur surga ('paradise mud cake'), shares only part of the name: it is a steamed pandan cake topped with coconut custard. Classic kue lumpur is the potato version described here.

ii. How kue lumpur stays soft and custardy

Kue lumpur sits between a cake and a custard. The batter is very loose — much thinner than a cake batter — and contains a large amount of liquid, coconut milk, relative to the small amount of flour. Mashed potato adds body, moisture and starch; eggs set the batter; butter adds richness. Cooked gently, it sets into a soft, moist, slightly wobbly cake that is creamy rather than spongy.

The potato must be completely smooth. Lumps of potato remain as lumps in the cake; pressing the hot potato through a ricer or sieve, or mashing it thoroughly while warm, gives a velvety batter. A floury potato is best, as waxy potatoes become gluey when mashed.

Traditionally kue lumpur is cooked on the stove in a heavy cast-aluminium cetakan kue lumpur, a pan with round, shallow moulds, covered with a lid. The batter sets from the bottom up, forming a golden base and edges, while the lid traps heat to set the top. The raisins are added once the surface has started to set, so they sit on top rather than sinking. In the oven, a mini muffin or tartlet tin gives very similar results, with a lightly browned top.

Gentle heat keeps the texture custardy. Too high and the cakes puff, crack and become dry and spongy; the eggs in the batter overcook before the centre sets. They are ready when the surface is set and springs back lightly, but the centre is still very soft.

iii. Ingredients

Makes 16 servings · scroll the side panel to adjust

• 250 g floury potatoes, peeled
• 400 ml coconut milk
• 2 pandan leaves, knotted
• 100 g caster sugar
• ½ tsp salt
• 75 g butter, melted
• 3 eggs, at room temperature
• 100 g plain flour
• 1 tsp vanilla extract
• 40 g raisins
• 1 tbsp butter or oil, for greasing

Use a floury potato such as Maris Piper or russet; waxy potatoes make a gluey batter. Some cooks use sweet potato or purple sweet potato for colour. Full-fat coconut milk gives the classic rich flavour; the pandan scents it gently. Butter is standard in modern recipes, though many cooks use margarine. Raisins are the traditional topping; grated cheese, sliced jackfruit or chocolate chips are popular alternatives.

iv. Method

1. Boil or steam the potatoes until completely soft, about 15 minutes. Drain well and press through a ricer or sieve, or mash until perfectly smooth. Weigh out 200 g of purée.
2. Warm the coconut milk with the pandan leaves over low heat for 5 minutes, without boiling. Remove the leaves and cool until lukewarm.
3. Whisk the eggs, sugar and salt until the sugar dissolves and the mixture is slightly frothy, about 2 minutes. Whisk in the potato purée, then the melted butter and vanilla.
4. Whisk in the flour, then gradually whisk in the coconut milk to make a smooth, thin batter. Strain if there are any lumps.
5. To bake: heat the oven to 180 °C (350 °F), or 160 °C fan. Grease a 24-hole mini muffin tin or 16 small tartlet moulds and heat in the oven for 5 minutes. Fill each three-quarters full and bake for 10 minutes, then scatter a few raisins on top and bake for 15–20 minutes more, until set and golden at the edges.
6. To cook in a kue lumpur pan: heat the greased pan over low heat, fill the moulds, cover and cook for 8–10 minutes until the surface begins to set, then add the raisins, cover again and cook for 5–8 minutes until set.
7. Leave to cool in the moulds for 10 minutes before lifting out with a small spoon or palette knife. Serve warm or at room temperature.

v. Tips & common mistakes

• Make the potato purée very smooth. Any lumps stay in the finished cakes.
• Expect a thin batter. It looks too runny for a cake; that is what gives kue lumpur its custardy texture.
• Stir before every fill. The potato and flour settle to the bottom of the bowl.
• Add the raisins once the top starts to set. Added at the start, they sink.
• Keep the heat gentle. High heat makes the cakes puff, crack and dry out.
• Let them rest before unmoulding. Warm kue lumpur is very soft and breaks if lifted too soon.

vi. Variations

Kue lumpur ubi uses sweet potato, and purple sweet potato gives a vivid violet colour. Kue lumpur pandan adds pandan paste for green cakes. Modern toppings include grated cheese, popular in Indonesia with sweet cakes, chocolate chips, jackfruit and young coconut. Kue lumpur surga is a steamed pandan cake with a coconut custard layer and is a different recipe.

For other Indonesian snack cakes, see kue cubit, kue apem, serabi and kue putu. The Filipino bibingka and the Thai coconut pancakes khanom krok share the coconut-milk richness, and the Portuguese-influenced bebinca is another egg and coconut cake from a colonial meeting of cuisines.

vii. Serving & storage

Serve kue lumpur warm or at room temperature as an afternoon snack with tea or coffee, or as part of a tray of mixed kue for a gathering. They are rich and soft, so two or three per person is plenty.

They are best on the day they are made and keep covered at room temperature for a day. In the fridge they keep for up to 3 days but firm up; warm them for 10 seconds in a microwave or steam for 3–4 minutes before serving. They do not freeze well, as the custardy texture turns watery.

ix. More from Indonesian & Malaysian

• Kue Cubit — Indonesian pinch cakes
• Kue Apem — steamed rice cakes
• Serabi — coconut pancakes
• Kue Lapis — layered steamed cake
• Bibingka — Filipino rice cake
• Bebinca — Goan layered coconut cake