Whenever I make bao, there’s always a point where I have to decide: Do I cook the bao with the pleats facing up or down? Sometimes, the dumpling dictates the direction. For example, Shanghai soup dumplings (xiao long bao) have been engineered to be cooked with the pleats up.
Steamed yeast-leavened bao can be cooked facing up or down. In general, however, savory bao are steamed with the pleats up whereas sweet bao are cooked with the pleats facing down. It’s a nice way to mark the different fillings. Some people use dots of food coloring to distinguish the various fillings. In those cases the bao are steamed pleats down.
On the other hand, when I mess up the pleats, an easy way to hide my mistake is to steam with the pleats facing down. Savory Filipino and Vietnamese bao are often steamed with the pleats down, for reasons that are more cultural than practical. Do you want puffy pleats on top? Or do you want a smooth domed finish?
On the left, is a bao steamed with pleats down. The pleats faced up on the right-hand bao.
For the steamed egg custard buns recipe, I did them both ways because I was tinkering with the filling recipe and needed to mark them; the drier looking bao filling on the left had less coconut milk than the one on the right. As you can see from the photo above, the major difference is that the filling is better centered in the bao that was cooked with the pleats facing down. There was more gathered dough below to support the filling.
That’s not always the case. Saucy and raw meat fillings get juicy during steaming and that moisture tends to slightly compress the bottom of the bao. Regardless of which direction the pleats faced during steaming, the bottom of those kinds of bao will not be as puffy as the top. Does that affect overall flavor? Nope.
When making baked bao, the pleats always face down. If the pleats faced up during baking, the bao may not stay closed. Oven heat is different than steam heat.
Sometimes you can choose which direction to point your pleats during cooking. Sometimes you can’t. Do you have a personal preference or guidelines you follow (or have observed)?