Mix corn starch, corn flour with salt in a bowl. Add the butter and knead into a crumbly dough, preferably with your hands. Add sugar or other sweetener (e.g. honey) and water. Knead quickly with your hands to form a smooth dough. Shape the dough into two rolls and wrap in cling film and place in the refrigerator for at least two hours.
Line a baking sheet with parchment paper. Cut the dough rolls into 1 cm thick slices and bake at 190 ° for about 10-15 minutes.