Mix the dry ingredients in your stand mixer or by hand using a whisk; flour, salt, baking powder, tapioca flour for a minute or two until combined
Mix in the egg
Start adding water to the mixture slowly while the mixer is on. First, the mixture might separate but keep your mixer on, and the dough will come together.
How to check the consistency of the dough? Take a small amount of dough and start to form a ball with your hands. Stop adding water as soon as the dough is not crumbly and you are able to form a ball,
Once you are happy with the consistency of the dough, knead it with the palm of your hand for a minute
Cut 10 pieces of 10cm*10cm / 4inches*4inches square shape baking papers.
Using a Digital scale form the dough into little balls about 7g each. I suggest working with very slightly wet hands so it won´t stick to your hands
Place 8 balls in a ring shape in a way that they are touching each other.
Once all the donut rings are ready (should be 10 all l together), heat vegetable oil in a saucepan to 170-180C / 338-356F
Place 2-3 donuts into the oil with the parchment paper on them. Flip the donuts after about 30 seconds and remove the parchment paper. Fry the donuts for 1-2 minutes on each side, or until golden brown
Remove the donuts once they are golden brown onto a plate with paper towel on it
Using a themormeter check the temperature of the oil every now and then and adjust the heat if necessary. It is very important that the oil temperature is correct on order to not to burn the donuts or not to bake them too oily
Let the donuts come to room teperature before glazing