Thanks for asking! I found the recipe, but I really don't think the one I had had any sugar, it seemed like it was made with dehydrated bananas-probably sun dried- quite common in the south of Vietnam. Also I did not try it with the mung bean paste, but it's all here.

Also the names are:
Bánh Chuối Hấp - Steamed Banana Cake
Nước Cốt Dừa - Coconut Sauce

http://vietspices.blogspot.com/2010/01/banana-mung-bean-durian-with-coconut.html?m=1