Although the banh xeo batter is vegan, the fillings are usually not vegan.  So, if you order these savory Vietnamese crepes in Vietnamese restaurants, or, indeed, on the streets of Vietnam, then it would usually contain pork belly strips and/or prawns as well.  Likewise, the nuoc cham dipping sauce would usually contain fish sauce as well, which makes it non-vegan.  This recipe, however, has been adapted to be vegan and just as delicious!