How to make sweet rice rolls with mung bean filling /Cambodian Nom terk chek

Sweet rice rolls We call these Nom terk chek in Khmer Ingredients 1 1/2 cups of sweet rice flour 1/2 cup of tapioca starch 1/2 cup of sugar 1/4 tsps. of salt 1 1/2 cup of water (use only 1 cup to make the firm Dough than this) 1/4 cup of coconut milk 2 tbsps. of vegetable oil Steam the batter mixture about 20 minutes or until it have no running batter when we poke it .