19 June 2012

Bubble Tea Cake!

In the evening of the 19th day of the 6th month of the 2012 year since the flying spaghetti monster was born, PIE-314 invented bubble tea cake.

Tea flavoured cake with tapioca pearls. In my previous blog post (Bubble Tea Cookies), I talked about WHY I put bubble tea bubbles (henceforth referred to as "tapioca pearls") in my baking. In short, I had a dream a bunch of days ago in which I was icing a bubble tea shaped cake, with vibrant orange icing. The tapioca pearls had been cooked into the cake. I made tapioca pearl cookies yesterday to see whether tapioca pearls could be baked, AND THEY CAN!

So, today, I made a spongy, chewy cake to match the texture of the tapioca pearls inside (actually, I made two by accident, since most of this was improvised). Excuse me for the imprecise measurements; as I am subletting in Philadelphia, I lack a lot of my kitchen tools.

UPDATE: I improved the recipe on the 24th of June, so go there for the recipe! I've crossed out the things that don't apply anymore here.

INGREDIENTS for ONE 9-inch (23 cm) diameter round pan of cake that is about 3 cm in height
2 tbsp tea leaves (I used loose Pu-erh tea leaves, although traditional bubble tea uses black tea. You can use whatever you like)

1 large egg
1/4 cup of brown sugar
1/2 to 2/3 cup white sugar +/- some to suit your taste
1 tbsp oil (optional)
1.5 c flour (I actually used 1.25 c white flour and 0.25 c wheat germ. You can also use 1 c white flour and 0.5 c whole wheat flour)
0.5 tsp baking soda
2 tbsp vinegar (I used balsamic because that's all I had, but any vinegar should work)

1 dry cup of instant pearl milk tea (bubble tea) tapioca pearls
1 cup confectioner's (powdered) sugar
Bubble tea straw

METHOD (~1.5 hours total working calmly)
0. A few hours before you start the cake, heat up about half a pot of water and your tea  leaves (without sugar). Keep this on a small boil until the tea is beyond the desired strength. Then, pour out 150 ml and let it cool. Leave the rest of the tea in the pot. (I messed this up today; it should take at least 10 minutes)
A. Cake Batter!
1. Mix sugars, egg, oil (optional), and tea in a giant bowl.
2. Mix flour(s) and baking soda in another bowl.
3. Add 1/3 of the liquid stuff into the dry mixture and mix until there are no more lumps, using figure 8s. Add another 1/3, mix, and then add the last 1/3 and mix until smooth. You will have a batter that is a bit thicker than pancake batter. Leave this batter alone while you prepare the tapioca pearls. The batter will not taste good uncooked.

2. Tapioca Addition & Cake Batter!
4. Remove loose tea leaves from the pot, and pour tapioca pearls and one tbsp of brown sugar into the leftover tea. Turn on the heat to high. Cover for around 3-5 minutes, until all the pearls have risen to the top and taste good. 
5. Then, turn off the heat and fish out the pearls(I used a tea strainer). Fold them into the batter, trying not to get too much extra tea into the batter.
6. Grease your baking dish using a butter wrapper from your stash in the freezer!
7. Quickly fold the vinegar into the batter. You will hear a small hissing noise due to the vinegar reacting with the baking soda. When the vinegar is evenly incorporated, pour the cake mixture into your pan.

8. Bake in an unpreheated oven for 20 minutes at 350 degrees F on the middle shelf. Stick a fork into the cake, and if it comes out clean, it's cooked!

9. Place hot cake onto a cutting board. Alternatively, you can wait until the cake has cooled by cooling it on a metal cooling rack.

10. On the cutting board, place the rim of a glass jar on the cake and cut out a hexagon around the jar using a knife. Cut with all your strength, as the tapioca pearls are really sticky! Cut four of these hexagons (yes, it's possible!).

11. Trim each hexagon into a circle. Preferably, each circle gets a tiny bit smaller (to emulate a bubble tea cup).

3. Cake Assembly version I
11. In a mug, mix 2 tbsp tea with 1 c of confectioner's sugar to make a tea glaze.
12. Place the circular cakes on top of each other on a pretty plate, starting with the smallest. Spoon glaze between each layer (yes, it drips!).

13. Glaze the top of the cake, then stick your bubble tea straw through all four layers so that your cake won't topple over.
14. Eat by grabbing off chunks by hand! Drink leftover tea! The cake must be consumed within a few hours. If left overnight, the tapioca balls will dry out, as do most tapioca products not submerged in liquid. (SP was hugging me while I took this photo; therefore, it is blurry)

4. Cake Assembly version II
11. Fill a (bubble tea) cup 3/4 of the way with bubble tea cake chunks (leftover from Assembly I or just... in general).
12. Add tea, sugar, and milk in whatever ratio you want. You should add the milk first if the tea is still hot.
13. Drink "bubble tea cake"-flavoured bubble tea (using straw to suck up the tapioca and cake)!

Possibly Helpful Notes:
The cake is unlike normal sponge cake, brownies, or normal bakery cake products. It is super chewy, EXTREMELY pliable (see image below - the cake bounces back to its original shape even after denting it with my spoon), gooey, and sort of gluten-y. It's a little like steamed cake, actually. Of course, you can substitute your own cake recipe for my recipe. However, the problem with using, say, a Victoria Sandwich cakewith tapioca pearls is that the pearls may sink to the bottom of the pan, and leave craters on the cake surface. Also, a bunch of butter cake recipes don't even need liquids. A muffin or quick-bread recipe may fare better.

I actually wanted to use 100% whole wheat flour for this recipe, but I was lugging some 10 pounds of food and drink back from Chinatown and Trader Joe's on one shoulder and one hand, and carrying an extra 5 pounds of flour for 30 minutes would've been quite unbearable. I don't know for sure scientifically, but I think that whole wheat flour would've made a thicker batter (more...fibre; more gelatinous? Cellulose maintains cell structure), and would've helped the tapioca pearls stay in the batter. I threw in some wheat germ for that and the sorta health reason. I am really glad that the pearls were well-distributed! Perhaps using 100% white flour would still render this result; I will try again once all this cake has been eaten. Note the dents in the bottom and tops, though.

I used way too much baking soda in my batter, and not enough sugar. Again, this was a "well-educated guess" recipe. I may actually just use 0.5 tsp of baking soda next time, and see whether I get the same amount of rise. However, to mask the baking soda taste (although SP can't taste it), you can just use Assembly method II and smother it with sugar, tea, and milk.

To obtain loose leaf tea, tapioca pearls, and bubble tea straws, go to Chinatown! :) I got my straw at Mayflower bakery after buying a delicious snowball (red bean paste inside rice mochi thing that has the texture of an Invisibility cloak, that promptly got squashed on the way back). I also didn't have much counter space. The green parts of the kitchen are all occupied areas. :(

I am extremely satisfied to be the first (at least, I think/hope I am) to document on the internet the incorporation of tapioca pearls into a baked cake.

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