Cantonese White Sugar Cake (白糖糕)

This is a popular dessert served in most, if not all, Cantonese Dim-Sum places.  This cake, seemingly easy to make, presents some challenges that might be both interesting and intriguing.  The cake must be soft and springy in its texture, and the cross section of the cake is expected to look like a two-layered sponge (see the end of Step 2 for more details of the layers).   It took us about a dozen tries to come up with a reliable and repeatable method below.  Hope it works in your kitchen as well!

1. [Mix Rice Powder] In a 4-cup measuring cup (or a small mixing bowl), add 1 1/2 cups of rice flour (粘米粉).  Gradually add 1 cup of hot, but not boiling, water into the measuring cup (bring water to hissing, but not boiling, and let cool for ~30 seconds; water temperature must be below 200 degF;  we use 195 degF water from a water boiler & warmer. Important- rice flour curdles around 212 degF).  Stir and mix evenly, with a pair of chopsticks, into thick paste form.  Note- Next time, will add 3 Tbsp of Water Chesnut Flour (grind first, if not in powder form).  Also, see left-side image in the picture for the product package, i.e., the Rice Flour, with labels in Red Letters. Please take care NOT to use the Glutinous Rice Flour, 糯米粉, i.e., the package with labels in Green Letters.
2. [Add White Syrup] In a 1-cup measuring cup, add 1/2 cup of hot, but not boiling, water first, then add 1/2 cup of sugar, stir until the sugar is fully dissolved.  Pour the water+sugar mix into the rice-flour+water mixture above, stir and mix evenly for 2-3 minutes (until it is about as thick as heavy cream, with no clumps anywhere).  This process produces almost-cooked "rice milk" (半熟米漿).  Let it sit and cool down to lukewarm to the touch, around 100-degF, i.e., slightly warmer than body temperature (for about 30 minutes).  Note- Most of the online recipes for this cake apply direct heat under the rice flour+sugar+water mixture (by stirring constantly and taking the pot off heat frequently), where the mixture could curdle without much a sign of warning, because rice flour curdles around 212 degF, i.e., the boiling point for water.  If your water is too hot and the rice flour curdles, add 1/4 cup of water and stir for a minute or two to get the lumps fully dissolved (add another 1/4 cup of water and stir again if the rice flour is still too thick; need to be as thick as heavy cream, not as thick as paste), and the end product will have honeycomb-like small holes throughout (see picture below), unlike what we produced here with two layers (a top layer with honeycomb pattern and a bottom layer with vertical-line-pattern, see end of this post for a picture).

   

   Not a two-layered sponge

3. [Proof Yeast] In the same 1-cup measuring cup used in Step 2, add 2 Tbsp of water (i.e., half of 1/4 cup), 1/2 tsp of sugar and 1 tsp of yeast (use Original type yeast, not the Instant Rising type) into the cup.  Stir and mix evenly.  Cover the measuring cup with plastic wrap and let sit for 5-10 minutes. If the yeast mixture foams up to ~1/4 cup mark of the measuring cup, the yeast is "proven" to be active and usable.  Add 1 tsp of baking powder into the yeast mixture, stir and mix thoroughly.  Now, pour the resulting mixture into the 4-cup measuring cup with "rice milk" (created in Step 2).  Stir and mix evenly for a minute or two.   Cover the measuring cup tightly with plastic wrap. 
4. Let the 4-cup measuring cup sit in a warm room-temperature environment (~68 degF or higher) for 3 hours, until foam wells up nicely.  Note- Consider using an artificially created warm environment for the yeast to do its magic: Set oven temperature to 200-degF, turn on oven for 1-1.5minutes, and leave the 4-cup measuring cup in the oven for 1.5 hours.
5. Add 1/2 tsp of veggie oil into the mixing bowl, stir and mix evenly.  Oil a 9" or 10" glass pan (or any bakeware that's suitable for steaming).  Carefully pour the content in the mixing bowl into the glass pan (the content should be 1/2"-3/4" thick).  Let the glass pan sit for another 5-10 minutes, while turning on heat for the steamer (needs at least 1" water for the 25 minutes of steaming in the next step).  Note- Will try 1-2 tsp veggie oil next time.
6. Steam the glass pan for 25 minutes (under consistent full-steam, by staying on medium-to-high heat).  The cake should rise up a bit, by ~1/4" (to 3/4"-1" thick)
7. Take the glass pan out, let it cool.  Cut and serve.  The cake will keep for a couple of days under room temperature (cover with plastic wrap after it's cool).  The cake becomes harder if refrigerated, and it needs to be heated in the microwave, then serve.  Here is the outcome from our kitchen.