Bika Ambon

The Bika Ambon cake is an Indonesian dessert made primarily of tapioca flour (extracted from cassava roots), yeast, coconut milk, eggs, and sugar, typically flavored with pandan, lemongrass and keffir lime leaves (which also make the cake quite fragrant). When baked, bubbles created by the yeast creates the spongy/honeycomb texture throughout the cake. There are similarities to several other cassava-based cakes in the Southeast Asian region: the Bika Ubi cake (more popular in Malaysia), and the Vietnamese Pandan Honeycomb cake (Banh Bo Nuong). Similarities could even extend to the Brazilian cassava cake - which makes sense, since the cassava plant originated from South America, and some say that the Portuguese introduced the cassava (the plant from which the tapioca flour is made) to Asia.

The honeycomb structure itself could actually be inspired by the Chinese "White Sugar Sponge Cake" or "Bai Tang Gao / Pak Thong Koh / Bak Tong Gou", which is made from rice & rice starch and leaven by the yeast created by the fermentation of the rice. Indeed, the Bika Ambon cake in the past was leavened by "tuak nira/enau" or fermented palm wine/rice wine yeast (wine is soaked into batter overnight, as wine further ferments to create the yeast, I suppose).

An interesting trivia about Bika Ambon: The cake supposedly originated in the city of Medan, in North Sumatera (which is the North-Western-most part of Indonesia), or at the very least it was originally popularized there among the Chinese communities in the city. Yet the word "Ambon" refers to the name of another Indonesian island located in the Eastern part of Indonesia, far away from Medan, where the cake is not at all popular).
One theory is that the cake was first sold / made popular by a shop located on a street in Medan called "Ambon street".  I have my own theory: Bika/Bingka means cake in Malay language (Sumatera is close to Malaysia, and a majority of Indonesian words are derived from the Malay vocabulary), and apparently Malaysia has a similar cake that is called Bika/Bingka Ubi (Ubi means cassava). By extension, could Ambon be another word for Ubi, in some more obscure Malay dialect? Indeed, I stumbled upon this website that says the word "ambon" actually translate to "ubi" in the Sasak language (a dialect spoken in Lombok, another Eastern-Indonesia Island), and the Sasak language is also primarily derived from a certain strain of the Malay language. Our could Ambon mean something else in Hokkien or Teochew (the dominant dialect used by Chinese community in Medan).  Anyways, it's a mystery probably not worth solving, though it does tickle the mind.

Like the Sweet Martabak (recipe link here), another Indonesian dessert with honeycomb-like texture (though the main bubble creating agent there is the baking powder), the Bika Ambon cake has frustrated many home bakers. Many wonder whether it depends on the ingredients, the freshness of the coconut milk, etc etc.

I personally hypothesize that, like with the Sweet Martabak, the key is bottom heat, to push the many bubbles created by the yeast (in Bika Ambon's case) in one direction, that is up. With the Martabak it is easier, because cooking uses a pan that is heated on the stove (basically from the bottom). But with a fan oven, it's rather tricky, because the heat is trapped in a contained environment and therefore spread throughout the oven.  A way that seems to work to get around this is: 1) Put pan on your lowest oven shelf to ensure proximity to bottom-heat element and focus of heat on pan bottom. (pre-heating pan for 15 mins before filling with batter, could also help further). 2) Open oven door to allow rising heat to escape, rather than accumulate above pan.  See this video showing a commercial production of Bika Ambon in Medan.

My first foray into this has been relatively satisfactory, in terms of achieving the texture and taste.  The taste and softness of the cake made me happy, I would say is nearly as good as ones I had back home in Indonesia.

I used a recipe by the venerable Miss Kitchen Tigress, whose detailed instructions on all the recipes I've tried, have been on the spot!  I also liked the simplicity, in that it doesn't require a separate sponge mixture, like some other recipes. The only modifications I made were adding lemongrass and keffir lime flavoring and slightly more pandan juice, and opening the oven door slightly ajar during the first stage of the baking.

Steeping lemongrass & keffir limes into coconut milk to add flavoring/aroma

I did have a near-disaster, though totally unrelated to the recipe.  I stupidly used a leaking springform pan (which size was actually more appropriate for the recipe), and unfortunately, the batter started dripping to the oven floor and smoke started to come out of the burnt drippings!!! Panic ensued!!! I was in a panicky dilemma of doing the more rational thing of turning off the oven to clean the drippings and just continuing baking for want of not wasting batter and fearing that interrupting the process would jeopardize the possibility of achieving the honeycomb structure!  Kids, in any situation, always choose the rational though, which thankfully I did, some minutes after the smoke started to become more noticeable (I shouldn't have waited that long though).  Also, lesson learnt, line bottom of your spring-form with aluminium or something. Anyways, I cleaned the oven, pre-heated again, transferred the batter to a 9x5 loaf pan, which was way too big (batter was still in liquid form after 10 minutes in the oven, the leaking probably prevented it from setting. Put back the loaf pan into the oven and restarted baking...and cake turned out great.....except that, a) lost half of the batter due to the leak and b) forgot to oil the loaf pan (I did oil the first spring form pan). That's why the photo shows what looks like shreds of thin cakes (bits of cake got stuck to pan when I tried to remove). The typical shape of cake should look more like the one shown in KitchenTigress' website.

Green-ish color from the pandan juice, honeycomb structure visible

Bika Ambon Recipe

Adapted from KitchenTigress.  Tips for creating natural Pandan Juice from Jun-Blog
Makes a 6x6x2 inch square pan (or 7inch round pan or 8x4 inch loaf pan)

Ingredients:
85 g sago or tapioca starch (2/3 cup + 2 tsp).  Tapioca flour = Tapioca starch.
1/4 tsp salt
3/4 tsp active dry yeast
145 g eggs (3 large eggs)
280 ml diluted coconut milk (reduced to 140 ml, see heating directions below) - Fresh or instant is fine. I used Kara pasteurized.
85 g sugar (1/3 cup + 2 TBSP)

Aromatic flavoring/color:
3 pandan leaves (cut into 4 inch pieces)
1 lemongrass stalk (bruise with side of knife and remove outermost layer, then tie into a knot)
5-10 keffir lime leaves (I used 1.5 keffir lime juice + rind instead. You can probably also use normal lime)(optional)
2 TBSP pandan juice for color (Directions below. You can also use pandan paste instead, probably smaller portion).
 >>All these are typical of an Indonesian Bika Ambon, but can be replaced by either orange juice/lemon juice/commercial pandan paste extract. Some people also use a bit of tumeric to achieve a bright yellow color, which is the more typical color of the cake.

Silvered/sliced almonds for garnishing.

Directions: 

1. Place keffir lime leaves and knotted lemon grass and pandan leaves, into coconut milk in a pan. Heat over medium heat until gentle boil (will take about 15 mins uncovered), then reduce to lowest heat and simmer for 15-20 minutes. Remove leaves & lemongrass, and strain coconut milk to yield the requisite 140ml liquid. 
2. Make pandan juice: Clean pandan leaves steeped earlier with tap water; cut into small pieces using scissors and place into blender with 1/4 cup boiling water; pulse some 10 seconds until blended. Strain juice (discard pulp), use 2 TBSP to add into reduced coconut milk. Mix thoroughly. 
3. Mix tapioca starch, sugar, salt and dry yeast. Add eggs and slowly whisk till smooth. 
4. Stir tapioca batter, while slowly pour coconut milk mixture into batter. 
5. Cover batter and set aside until batter is full of tiny bubbles, about in the summer 2½-3 hours (I put the bowl in a pre-warmed microwave to simulate this). 
6. After this starch will have settled to the bottom of the batter. Scrape and loosen starch in bottom of bowl and stir till just evenly mixed. 
7. Preheat oven to 160°C (320 F). Oven should be ready at the same time as batter. Line 15 x 15 x 5 cm cake pan with 25 x 25 cm parchment paper (You can also use a 8x4 inch loaf pan instead). Pour batter into cake pan.
   (I only had a 9x5inch loaf pan, which was way too big, so the cake came out too thin as you can see in the pic. I also ran out of parchment paper and forgot to oil the pan, so some of the cake stuck to the pan, even though it is non-stick. So, if you don't have parchment paper, make sure you lightly oil or butter your pan)
8. Place pan on bottom-most rack of oven and LEAVE OVEN DOOR SLIGHTLY AJAR (gap with wooden spoon). Bake this way until batter doesn't jiggle when shaken, about 25-35 minutes (you would see many bubbles/holes crowding the surface, they begin to appear at the 15 min mark). 
9. Then increase temperature to 180°C (350 F) and move cake to middle of oven. You can sprinkle some silvered almonds/sliced almond on cake surface at this point. Then CLOSE OVEN DOOR. Continue baking until surface is golden brown, another 10-15 minutes or so. 
10. Remove from oven. Unmould by lifting parchment paper. Leave cake on wire rack till cold.

Probably best to store cake in refrigerator due to coconut milk content. When cold, cake may seems a bit hard/rubbery, but the cake reheats very well; just pop in a slice into microwave for some 20 seconds, and cake will be a soft and spongy as if freshly baked.