In a small bowl, combine mozzarella, Parmesan, and feta. Set aside.

In a small saucepan, heat milk, butter, and salt. Bring to a boil while stirring gently and let it simmer. Some of it will evaporate, and that’s good. Remove from heat and let cool five to 10 minutes.

When cool, gradually add to the tapioca while mixing. Make sure it doesn’t get too liquidy.

Add one egg and mix again.

Add cheese mixture and mix until smooth. You should be able to roll it into balls. If dough is too wet, add a little more tapioca flour.

Form balls slightly larger than golf balls (about 30).

Place on parchment-lined baking sheet and bake at 400 degrees Fahrenheit for 15–20 minutes, until golden.