Into a baking tin, add the tapioca starch and spread evenly, bake in a preheated oven at 200°C (392°F) for 20 minutes or until it starts to crack. Crush it by hand into smaller pieces, add the milk, the butter, the salt and the egg. Mix it all together very well by hand, until a smooth dough is formed.
Get a piece of this dough, flatten it a bit, fill it to taste, close the dough and shape it into a circle. Repeat this process until you've used all the dough.
Butter a grill or sandwich maker (it can also be baked in the oven), and toast until golden brown.