In a bowl, add all dry ingredients together and whisk thoroughly.
Add butter, shortening, vinegar and yogurt.
Cut the wet ingredients into the dry until you can mold it like clay.
With your hands form it into a ball; refrigerate for at least 1 hour.
Roll dough according to your recipe.
Generously dust a flat clean surface with tapioca starch.
Cut dough into 10 equal parts.
Leave one part out and refrigerate the others until needed.
There is no need to cover the dough, as it does not dry out easily.
Generously dust a large smooth flat surface with tapioca starch.
Flatten a piece of dough and dust the top with tapioca starch.
Roll the dough out to about 1/8″ thick or less.
Lift dough from underneath with a sharp knife.
Dust surface again and turn dough over; cut into a 4×4″ square.
In one half of the square near a corner, add 1+ tablespoon of custard, or a filling of your choosing.
Fold the other side over the top of the filling, creating a triangle shape.
You may use a pastry edger to create scalloped edges.
Add parchment paper to a baking sheet.
Spray parchment lightly with olive oil; bake for 15 minutes.
Increase temperature to 375°F and bake for an additional 12-16 minutes.
TIP: Patch any cracks with water and/or additional dough or tapioca flour.