Whisk together all the dry ingredients in a large bowl.
Add the butter, yoghurt and boiling water and use a spoon to quickly stir the dough together. Quite quickly, it should become a moist but cohesive dough that you can pick up (be careful though, it will be hot!). Use the boiling water conservatively and add more if needed to form a dough that is moist but not overly sticky or wet. The dough should be moist and feel a little bit elastic. If it doesn't feel elastic at all, add more boiling water a little at a time.
Allow the dough to sit for a minute or so, then place onto a dry clean bench top. Knead for a minute or just until it forms a smooth, moist ball of dough. Cover with the bowl you mixed it in for 2-3 minutes
Flour a bench top with tapioca flour. Divide the dough into 7-8 balls. I find these tortillas are best when made really thin – they are more flexible and less doughy.
Take the first piece of dough and roll it out as thin and wide as you can. Use a large mixing bowl with a sharp lid or a spring-form cake tin edge to cut a circular tortilla out of your dough. I aim for 25-30cm large. Make sure the dough is larger than the bowl before you cut. Press down and wriggle gently to ensure a clean cut.
Gather the scraps back into the dough and repeat with the remaining dough until you have all your tortillas.
Preheat a large skillet or frypan over a medium heat. Once hot, add a scant amount of ghee or oil if you're using it. Add the first wrap and cook for 1-2 minutes before flipping to cook on the other side.
The tortilla should look cooked through and have some lightly browned spots. Repeat with the remaining tortillas, stacking them on a cooling rack as they cook to keep them soft and flexible. If you find them too crunchy after cooking, microwave them to loosen them up.
Store leftovers in an airtight container in the fridge. To use, simply microwave or heat in a steamy oven to restore their flexibility. See notes for freezing.