Blend all Part B ingredients in a blender until very smooth. Pour this mixture into the bowl from step 1 and mix well with a spatula until fully combined (no need to strain the batter).

Cover the bowl and let the batter rise in a warm place for 1.5 to 2 hours, or place it in the sun for 1 hour, until it doubles in size. Check occasionally, as it may rise faster than expected.

Fill a tall pot with water and bring to a strong boil. When the water is boiling, stir the batter again, then pour it into the prepared pan (no need to preheat the pan, but grease it to prevent sticking). For a 9.5-inch (24 cm) round pan, steam for 25 minutes: leave the lid slightly open for the first 10 minutes to release steam, then cover and steam for another 15 minutes. Turn off the heat, leave the cake in the pot with the lid open for 5 more minutes to dry the surface. Test doneness by inserting a toothpick—if it comes out clean, the cake is done. Let the cake cool before removing from the pan.

Note: For best results, use aluminum or tin pans. Avoid opening the lid frequently while steaming. This recipe makes one large 9.5-inch (24 cm) round cake. This version of bánh bò is soft and moist inside, without the honeycomb texture found in other types.