Place tapioca flour into a stand mixer or large bowl.
Pour milk, water and olive oil into a saucepan and bring to a boil.
Remove the saucepan from the hob and pour the hot liquid over the tapioca flour. Beat the mixture on medium-high speed for about 10 minutes until very sticky and cooled.
Add the egg and salt and beat in for a couple of minutes until the mixture is glossy and smooth.
Add the mozzarella and cheddar a little at a time until completely mixed in.
Using a spoon, divide mixture into 4 greased tart tins and bake for 25-30 minutes until golden.
Remove the rolls from the tins straightaway onto a cooling rack.
*It is not imperative to use tins to bake these rolls, you can just spoon the mixture and bake them directly onto a baking tray lined with greaseproof paper but it does ensure the rolls achieve the desired size.*The rolls are delicious eaten directly from the oven and should really be eaten the same day. You can wrap them in foil once cooled and enjoy them the following day too but they get stale quite quickly.*Recipe adapted from Olivia's Cuisine and BBC Good Food