A couple years ago when I put together my guide of Vietnamese Banh (linked below), I was confused about the difference between Banh Uot (opaque rice flour rolls), and Banh Cuon (translucent rice flour rolls) especially because there is also Banh Uot Thanh Tri and Banh Cuon Thanh Tri (rice flour sheets). Carb Lover's post about the chain Banh Cuon Tay Ho got me wondering about the differences again.
Photos of these 3 banh are below. I think Ive figured out the differences, but I may be wrong so anyone with more knowledge than me, please chime in.
Heres my take:
To start with Banh Uot translates to Wet Banh. Banh Cuon translates to Rolled Banh. And Thanh Tri translates to something like Threads or Strings. All three are made of water and finely ground rice flour, and thats where the similarities end. Heres what I think are the differences:
First, the wrapper: The wrapper for Banh Uot is a thicker version of the wrapper for Banh Cuon, and they have different fillings, and Thanh Tri is basically just the non-rolled, non-filled wrappers.
Im guessing the wrapper for Banh Uot is made by pouring the batter into an oiled pan, filling the pan bottom completely, whereas the wrapper for Banh Cuon is made by pouring the batter over a piece of cloth that is stretched tight across a steamer, so the end product is a translucent and ultra-thin. You can make banh cuon wrappers with a nonstick pan, but you have to pour the batter as thin as possible, and even then the texture wont be 100% right. And if you pour it too thickly or if the wrapper doesnt come out right, you gather the bad ones into a pile, and you have Banh Uot Thanh Tri or Banh Cuon Thanh Tri! Now Im really guessing.
Then the filling: Banh Uot is usually filled with marinated grilled pork (thit nuong) and (sometimes) Chinese lapseung sausage, and green leaf lettuce. Banh Cuon is usually filled with ground pork and thinly sliced cloud ear fungus.
Then the dipping sauce: Dark brown peanut dipping sauce for Banh Uot, and fish-sauce-based nuoc cham for Banh Cuon. Then there are the accompaniments: none for banh uot, and many possibilities for banh cuon, including banh cong which is another banh I need to add to my banh guide.
Okay. I think thats it. If this is correct, I can update my Banh Guide.