Preheat the oven to 350℉ / 180℃
Line a 8 x 8 inch baking tray with parchment paper or spray with oil
Mix all the ingredients for the crust together
Take ⅔ of the crust and press against the bottom of the baking tray
Bake for 10 minutes
Meanwhile, put all the ingredients for the filling, except the tapioca flour, in a pan and bring to a boil over medium heat while stirring often
Turn the heat down and leave to simmer around 15 minutes stirring occasionally
By the end of cooking the filling, add the tapioca flour and continue stirring until there are no lumps
Pour over the crust and spread evenly
Sprinkle the remaining ⅓ of the crust on top
Bake for 15 - 20 minutes based on the strength of your oven (you'd want to have a nice brown top)
Cool for about an hour at room temperature and around 2 hours in the fridge before serving